@table @emph
@item Overall Options
@xref{Overall Options,,Options Controlling the Kind of Output}.
-@gccoptlist{-c -S -E -o @var{file} -pipe -pass-exit-codes @gol
+@gccoptlist{-c -S -E -o @var{file} -combine -pipe -pass-exit-codes @gol
-x @var{language} -v -### --help --target-help --version}
@item C Language Options
-trigraphs -no-integrated-cpp -traditional -traditional-cpp @gol
-fallow-single-precision -fcond-mismatch @gol
-fsigned-bitfields -fsigned-char @gol
--funsigned-bitfields -funsigned-char @gol
--fwritable-strings}
+-funsigned-bitfields -funsigned-char}
@item C++ Language Options
@xref{C++ Dialect Options,,Options Controlling C++ Dialect}.
-Wno-multichar -Wnonnull -Wpacked -Wpadded @gol
-Wparentheses -Wpointer-arith -Wredundant-decls @gol
-Wreturn-type -Wsequence-point -Wshadow @gol
--Wsign-compare -Wstrict-aliasing @gol
+-Wsign-compare -Wstrict-aliasing -Wstrict-aliasing=2 @gol
-Wswitch -Wswitch-default -Wswitch-enum @gol
-Wsystem-headers -Wtrigraphs -Wundef -Wuninitialized @gol
-Wunknown-pragmas -Wunreachable-code @gol
-Wunused -Wunused-function -Wunused-label -Wunused-parameter @gol
--Wunused-value -Wunused-variable -Wwrite-strings}
+-Wunused-value -Wunused-variable -Wwrite-strings @gol
+-Wvariadic-macros}
@item C-only Warning Options
@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol
-feliminate-dwarf2-dups -feliminate-unused-debug-types @gol
-feliminate-unused-debug-symbols -fmem-report -fprofile-arcs @gol
-frandom-seed=@var{string} -fsched-verbose=@var{n} @gol
--ftest-coverage -ftime-report @gol
+-ftest-coverage -ftime-report -fvar-tracking @gol
-g -g@var{level} -gcoff -gdwarf-2 @gol
-ggdb -gstabs -gstabs+ -gvms -gxcoff -gxcoff+ @gol
-p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol
-foptimize-sibling-calls -fprefetch-loop-arrays @gol
-fprofile-generate -fprofile-use @gol
-freduce-all-givs -fregmove -frename-registers @gol
--freorder-blocks -freorder-functions @gol
+-freorder-blocks -freorder-blocks-and-partition -freorder-functions @gol
-frerun-cse-after-loop -frerun-loop-opt @gol
-frounding-math -fschedule-insns -fschedule-insns2 @gol
-fno-sched-interblock -fno-sched-spec -fsched-spec-load @gol
-mcmodel=@var{code-model} @gol
-m32 -m64 -mapp-regs -mno-app-regs @gol
-mfaster-structs -mno-faster-structs @gol
--mflat -mno-flat -mfpu -mno-fpu @gol
--mhard-float -msoft-float @gol
+-mfpu -mno-fpu -mhard-float -msoft-float @gol
-mhard-quad-float -msoft-quad-float @gol
-mimpure-text -mno-impure-text -mlittle-endian @gol
-mstack-bias -mno-stack-bias @gol
-munaligned-doubles -mno-unaligned-doubles @gol
--mv8plus -mno-v8plus -mvis -mno-vis @gol
--mcypress -mf930 -mf934 @gol
--msparclite -msupersparc -mv8}
+-mv8plus -mno-v8plus -mvis -mno-vis}
@emph{ARM Options}
@gccoptlist{-mapcs-frame -mno-apcs-frame @gol
+-mabi=@var{name} @gol
-mapcs-26 -mapcs-32 @gol
-mapcs-stack-check -mno-apcs-stack-check @gol
-mapcs-float -mno-apcs-float @gol
-msched-prolog -mno-sched-prolog @gol
-mlittle-endian -mbig-endian -mwords-little-endian @gol
-malignment-traps -mno-alignment-traps @gol
--msoft-float -mhard-float -mfpe @gol
+-mfloat-abi=@var{name} soft-float -mhard-float -mfpe @gol
-mthumb-interwork -mno-thumb-interwork @gol
--mcpu=@var{name} -march=@var{name} -mfpe=@var{name} @gol
+-mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol
-mstructure-size-boundary=@var{n} @gol
-mabort-on-noreturn @gol
-mlong-calls -mno-long-calls @gol
-mcheck-zero-division -mno-check-zero-division @gol
-mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol
-mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp @gol
--mfix-sb1 -mno-fix-sb1 -mflush-func=@var{func} @gol
--mno-flush-func -mbranch-likely -mno-branch-likely}
+-mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @gol
+-mfix-vr4120 -mno-fix-vr4120 -mfix-sb1 -mno-fix-sb1 @gol
+-mflush-func=@var{func} -mno-flush-func @gol
+-mbranch-likely -mno-branch-likely}
@emph{i386 and x86-64 Options}
@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
-mno-fp-ret-in-387 -msoft-float -msvr3-shlib @gol
-mno-wide-multiply -mrtd -malign-double @gol
-mpreferred-stack-boundary=@var{num} @gol
--mmmx -msse -msse2 -mpni -m3dnow @gol
+-mmmx -msse -msse2 -msse3 -m3dnow @gol
-mthreads -mno-align-stringops -minline-all-stringops @gol
-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
-m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer @gol
-mschedule=@var{cpu-type} -mspace-regs -msio -mwsio @gol
-nolibdld -static -threads}
-@emph{Intel 960 Options}
-@gccoptlist{-m@var{cpu-type} -masm-compat -mclean-linkage @gol
--mcode-align -mcomplex-addr -mleaf-procedures @gol
--mic-compat -mic2.0-compat -mic3.0-compat @gol
--mintel-asm -mno-clean-linkage -mno-code-align @gol
--mno-complex-addr -mno-leaf-procedures @gol
--mno-old-align -mno-strict-align -mno-tail-call @gol
--mnumerics -mold-align -msoft-float -mstrict-align @gol
--mtail-call}
-
@emph{DEC Alpha Options}
@gccoptlist{-mno-fp-regs -msoft-float -malpha-as -mgas @gol
-mieee -mieee-with-inexact -mieee-conformant @gol
-minline-int-divide-max-throughput -mno-dwarf2-asm @gol
-mfixed-range=@var{register-range}}
-@emph{D30V Options}
-@gccoptlist{-mextmem -mextmemory -monchip -mno-asm-optimize @gol
--masm-optimize -mbranch-cost=@var{n} -mcond-exec=@var{n}}
-
@emph{S/390 and zSeries Options}
@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
-mhard-float -msoft-float -mbackchain -mno-backchain @gol
-metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol
-mstack-align -mdata-align -mconst-align @gol
-m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol
--melf -maout -melinux -mlinux -sim -sim2}
+-melf -maout -melinux -mlinux -sim -sim2 @gol
+-mmul-bug-workaround -mno-mul-bug-workaround}
@emph{PDP-11 Options}
@gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol
-malloc-cc -mfixed-cc -mdword -mno-dword @gol
-mdouble -mno-double @gol
-mmedia -mno-media -mmuladd -mno-muladd @gol
+-mfdpic -minline-plt -mgprel-ro -multilib-library-pic -mlinked-fp @gol
-mlibrary-pic -macc-4 -macc-8 @gol
-mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move @gol
-mscc -mno-scc -mcond-exec -mno-cond-exec @gol
sort of output is being produced, whether it be an executable file,
an object file, an assembler file or preprocessed C code.
-If you specify @option{-o} when compiling more than one input file, or
-you are producing an executable file as output, all the source files
-on the command line will be compiled at once.
-
If @option{-o} is not specified, the default is to put an executable file
in @file{a.out}, the object file for @file{@var{source}.@var{suffix}} in
@file{@var{source}.o}, its assembler file in @file{@var{source}.s}, and
the assembler is unable to read from a pipe; but the GNU assembler has
no trouble.
+@item -combine
+@opindex combine
+If you are compiling multiple source files, this option tells the driver
+to pass all the source files to the compiler at once (for those
+languages for which the compiler can handle this). This will allow
+intermodule analysis (IMA) to be performed by the compiler. Currently the only
+language for which this is supported is C. If you pass source files for
+multiple languages to the driver, using this option, the driver will invoke
+the compiler(s) that support IMA once each, passing each compiler all the
+source files appropriate for it. For those languages that do not support
+IMA this option will be ignored, and the compiler will be invoked once for
+each source file in that language. If you use this option in conjunction
+with -save-temps, the compiler will generate multiple pre-processed files
+(one for each source file), but only one (combined) .o or .s file.
+
@item --help
@opindex help
Print (on the standard output) a description of the command line options
declaration does not use either @code{signed} or @code{unsigned}. By
default, such a bit-field is signed, because this is consistent: the
basic integer types such as @code{int} are signed types.
-
-@item -fwritable-strings
-@opindex fwritable-strings
-Store string constants in the writable data segment and don't uniquize
-them. This is for compatibility with old programs which assume they can
-write into string constants.
-
-Writing into string constants is a very bad idea; ``constants'' should
-be constant.
-
-This option is deprecated.
@end table
@node C++ Dialect Options
Therefore, the ABI obtained using version 0 will change as ABI bugs
are fixed.
-The default is version 1.
+The default is version 2.
@item -fno-access-control
@opindex fno-access-control
Give string constants type @code{char *} instead of type @code{const
char *}. By default, G++ uses type @code{const char *} as required by
the standard. Even if you use @option{-fno-const-strings}, you cannot
-actually modify the value of a string constant, unless you also use
-@option{-fwritable-strings}.
+actually modify the value of a string constant.
This option might be removed in a future release of G++. For maximum
portability, you should structure your code so that it works with
cases, but does attempt to catch the more common pitfalls. It is
included in @option{-Wall}.
+@item -Wstrict-aliasing=2
+@opindex Wstrict-aliasing=2
+This option is only active when @option{-fstrict-aliasing} is active.
+It warns about all code which might break the strict aliasing rules that the
+compiler is using for optimization. This warning catches all cases, but
+it will also give a warning for some ambiguous cases that are safe.
+
@item -Wall
@opindex Wall
All of the above @samp{-W} options combined. This enables all the
constants.) Note, these suffixes appear in macros defined in the system
headers of most modern systems, e.g.@: the @samp{_MIN}/@samp{_MAX} macros in @code{<limits.h>}.
Use of these macros in user code might normally lead to spurious
-warnings, however gcc's integrated preprocessor has enough context to
+warnings, however GCC's integrated preprocessor has enough context to
avoid warning in these cases.
@item
because these ISO C features will appear in your code when using
libiberty's traditional C compatibility macros, @code{PARAMS} and
@code{VPARAMS}. This warning is also bypassed for nested functions
-because that feature is already a gcc extension and thus not relevant to
+because that feature is already a GCC extension and thus not relevant to
traditional C compatibility.
@end itemize
@option{-Wlong-long} and @option{-Wno-long-long} are taken into account
only when @option{-pedantic} flag is used.
+@item -Wvariadic-macros
+@opindex Wvariadic-macros
+@opindex Wno-variadic-macros
+Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU
+alternate syntax when in pedantic ISO C99 mode. This is default.
+To inhibit the warning messages, use @option{-Wno-variadic-macros}.
+
@item -Wdisabled-optimization
@opindex Wdisabled-optimization
Warn if a requested optimization pass is disabled. This warning does
@item V
@opindex dV
Dump after the value profile transformations, to @file{@var{file}.13.vpt}.
+Also dump after variable tracking, to @file{@var{file}.35.vartrack}.
@item w
@opindex dw
Dump after the second flow pass, to @file{@var{file}.27.flow2}.
time spent executing operating system routines on behalf of the program.
Both numbers are in seconds.
+@item -fvar-tracking
+@opindex fvar-tracking
+Run variable tracking pass. It computes where variables are stored at each
+position in code. Better debugging information is then generated
+(if the debugging information format supports this information).
+
+It is enabled by default when compiling with optimization (@option{-Os},
+@option{-O}, @option{-O2}, ...), debugging information (@option{-g}) and
+the debug info format supports it.
+
@item -print-file-name=@var{library}
@opindex print-file-name
Print the full absolute name of the library file @var{library} that
@item -print-search-dirs
@opindex print-search-dirs
Print the name of the configured installation directory and a list of
-program and library directories gcc will search---and don't do anything else.
+program and library directories @command{gcc} will search---and don't do anything else.
-This is useful when gcc prints the error message
+This is useful when @command{gcc} prints the error message
@samp{installation problem, cannot exec cpp0: No such file or directory}.
To resolve this you either need to put @file{cpp0} and the other compiler
-components where gcc expects to find them, or you can set the environment
+components where @command{gcc} expects to find them, or you can set the environment
variable @env{GCC_EXEC_PREFIX} to the directory where you installed them.
Don't forget the trailing '/'.
@xref{Environment Variables}.
@option{-Os} disables the following optimization flags:
@gccoptlist{-falign-functions -falign-jumps -falign-loops @gol
--falign-labels -freorder-blocks -fprefetch-loop-arrays}
+-falign-labels -freorder-blocks -freorder-blocks-and-partition -fprefetch-loop-arrays}
If you use multiple @option{-O} options, with or without level numbers,
the last such option is the one that is effective.
@item -finline-limit=@var{n}
@opindex finline-limit
-By default, gcc limits the size of functions that can be inlined. This flag
+By default, GCC limits the size of functions that can be inlined. This flag
allows the control of this limit for functions that are explicitly marked as
inline (i.e., marked with the inline keyword or defined within the class
definition in c++). @var{n} is the size of functions that can be inlined in
@item -fnew-ra
@opindex fnew-ra
Use a graph coloring register allocator. Currently this option is meant
-for testing, so we are interested to hear about miscompilations with
-@option{-fnew-ra}.
+only for testing. Users should not specify this option, since it is not
+yet ready for production use.
@item -fno-branch-count-reg
@opindex fno-branch-count-reg
@opindex fno-guess-branch-probability
Do not guess branch probabilities using a randomized model.
-Sometimes gcc will opt to use a randomized model to guess branch
+Sometimes GCC will opt to use a randomized model to guess branch
probabilities, when none are available from either profiling feedback
(@option{-fprofile-arcs}) or @samp{__builtin_expect}. This means that
different runs of the compiler on the same program may produce different
Enabled at levels @option{-O2}, @option{-O3}.
+@item -freorder-blocks-and-partition
+@opindex freorder-blocks-and-partition
+In addition to reordering basic blocks in the compiled function, in order
+to reduce number of taken branches, partitions hot and cold basic blocks
+into separate sections of the assembly and .o files, to improve
+paging and cache locality performance.
+
@item -freorder-functions
@opindex freorder-functions
Reorder basic blocks in the compiled function in order to reduce number of
taken branches and improve code locality. This is implemented by using special
-subsections @code{text.hot} for most frequently executed functions and
-@code{text.unlikely} for unlikely executed functions. Reordering is done by
+subsections @code{.text.hot} for most frequently executed functions and
+@code{.text.unlikely} for unlikely executed functions. Reordering is done by
the linker so object file format must support named sections and linker must
place them in a reasonable way.
Enabled at levels @option{-O2}, @option{-O3}.
-@item -frename-registers
-@opindex frename-registers
-Attempt to avoid false dependencies in scheduled code by making use
-of registers left over after register allocation. This optimization
-will most benefit processors with lots of registers. It can, however,
-make debugging impossible, since variables will no longer stay in
-a ``home register''.
-
@item -fweb
@opindex fweb
Constructs webs as commonly used for register allocation purposes and assign
however, make debugging impossible, since variables will no longer stay in a
``home register''.
-Enabled at levels @option{-O3}.
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os},
+on targets where the default format for debugging information supports
+variable tracking.
@item -fno-cprop-registers
@opindex fno-cprop-registers
@item -fprofile-generate
@opindex fprofile-generate
-Enable options usually used for instrumenting application to produce profile usefull
-for later recompilation profile feedback based optimization.
-The following options are enabled: @code{-fprofile-arcs}, @code{-fprofile-values}, @code{-fvpt}
+Enable options usually used for instrumenting application to produce
+profile useful for later recompilation with profile feedback based
+optimization. You must use @code{-fprofile-generate} both when
+compiling and when linking your program.
+
+The following options are enabled: @code{-fprofile-arcs}, @code{-fprofile-values}, @code{-fvpt}.
@item -fprofile-use
@opindex fprofile-use
This option is experimental and does not currently guarantee to
disable all GCC optimizations that are affected by rounding mode.
-Future versions of gcc may provide finer control of this setting
+Future versions of GCC may provide finer control of this setting
using C99's @code{FENV_ACCESS} pragma. This command line option
will be used to specify the default state for @code{FENV_ACCESS}.
from profiling values of expressions and adds @samp{REG_VALUE_PROFILE}
notes to instructions for their later usage in optimizations.
+Enabled with @option{-profile-generate} and @option{-profile-use}.
+
@item -fvpt
@opindex fvpt
If combined with @option{-fprofile-arcs}, it instructs the compiler to add
Currently the optimizations include specialization of division operation
using the knowledge about the value of the denominator.
+Enabled with @option{-profile-generate} and @option{-profile-use}.
+
+@item -frename-registers
+@opindex frename-registers
+Attempt to avoid false dependencies in scheduled code by making use
+of registers left over after register allocation. This optimization
+will most benefit processors with lots of registers. Depending on the
+debug information format adopted by the target, however, it can
+make debugging impossible, since variables will no longer stay in
+a ``home register''.
+
+Not enabled by default at any level because it has known bugs.
+
@item -fnew-ra
@opindex fnew-ra
Use a graph coloring register allocator. Currently this option is meant
simplifies the control flow of the function allowing other optimizations to do
better job.
+Enabled with @option{-profile-use}.
+
@item -funit-at-a-time
@opindex funit-at-a-time
Parse the whole compilation unit before starting to produce code.
This allows some extra optimizations to take place but consumes more
memory.
+Enabled at levels @option{-O2}, @option{-O3}.
+
@item -funroll-loops
@opindex funroll-loops
Unroll loops whose number of iterations can be determined at compile time or
(i.e. complete removal of loops with small constant number of iterations).
This option makes code larger, and may or may not make it run faster.
+Enabled with @option{-profile-use}.
+
@item -funroll-all-loops
@opindex funroll-all-loops
Unroll all loops, even if their number of iterations is uncertain when
roll much (from profile feedback). It also turns on complete loop peeling
(i.e. complete removal of loops with small constant number of iterations).
+Enabled with @option{-profile-use}.
+
@item -funswitch-loops
@opindex funswitch-loops
Move branches with loop invariant conditions out of the loop, with duplicates
@option{-fold-unroll-all-loops} implies the same options as
@option{-fold-unroll-loops}.
-@item -funswitch-loops
-@opindex funswitch-loops
-Move branches with loop invariant conditions out of the loop, with duplicates
-of the loop on both branches (modified according to result of the condition).
-
-@item -funswitch-loops
-@opindex funswitch-loops
-Move branches with loop invariant conditions out of the loop, with duplicates
-of the loop on both branches (modified according to result of the condition).
-
@item -fprefetch-loop-arrays
@opindex fprefetch-loop-arrays
If supported by the target machine, generate instructions to prefetch
@item -fbtr-bb-exclusive
@opindex fbtr-bb-exclusive
-WHen performing branch target register load optimization, don't reuse
+When performing branch target register load optimization, don't reuse
branch target registers in within any basic block.
@item --param @var{name}=@var{value}
optimization will not be done.
@item max-gcse-passes
-The maximum number of passes of GCSE to run.
+The maximum number of passes of GCSE to run. The default is 1.
@item max-pending-list-length
The maximum number of pending dependencies scheduling will allow
@item max-inline-insns-single
Several parameters control the tree inliner used in gcc.
-This number sets the maximum number of instructions (counted in gcc's
+This number sets the maximum number of instructions (counted in GCC's
internal representation) in a single function that the tree inliner
will consider for inlining. This only affects functions declared
inline and methods implemented in a class declaration (C++).
@item max-cse-path-length
-Maximum number of basic blocks on path that cse considers.
+Maximum number of basic blocks on path that cse considers. The default is 10.
@item ggc-min-expand
feedback is available and may be set to higher values than
@option{reorder-block-duplicate} since information about the hot spots is more
accurate.
+
+@item max-sched-region-blocks
+The maximum number of blocks in a region to be considered for
+interblock scheduling. The default value is 10.
+
+@item max-sched-region-insns
+The maximum number of insns in a region to be considered for
+interblock scheduling. The default value is 100.
@end table
@end table
* MIPS Options::
* i386 and x86-64 Options::
* HPPA Options::
-* Intel 960 Options::
* DEC Alpha Options::
* DEC Alpha/VMS Options::
* H8/300 Options::
* AVR Options::
* MCore Options::
* IA-64 Options::
-* D30V Options::
* S/390 and zSeries Options::
* CRIS Options::
* MMIX Options::
this is much slower than calling the ABI library routines. Thus the
@option{-msoft-quad-float} option is the default.
-@item -mno-flat
-@itemx -mflat
-@opindex mno-flat
-@opindex mflat
-With @option{-mflat}, the compiler does not generate save/restore instructions
-and will use a ``flat'' or single register window calling convention.
-This model uses %i7 as the frame pointer and is compatible with the normal
-register window model. Code from either may be intermixed.
-The local registers and the input registers (0--5) are still treated as
-``call saved'' registers and will be saved on the stack as necessary.
-
-With @option{-mno-flat} (the default), the compiler emits save/restore
-instructions (except for leaf functions) and is the normal mode of operation.
-
-These options are deprecated and will be deleted in a future GCC release.
-
@item -mno-unaligned-doubles
@itemx -munaligned-doubles
@opindex mno-unaligned-doubles
This option is only available on SunOS and Solaris.
-@item -mv8
-@itemx -msparclite
-@opindex mv8
-@opindex msparclite
-These two options select variations on the SPARC architecture.
-These options are deprecated and will be deleted in a future GCC release.
-They have been replaced with @option{-mcpu=xxx}.
-
-@item -mcypress
-@itemx -msupersparc
-@itemx -mf930
-@itemx -mf934
-@opindex mcypress
-@opindex msupersparc
-@opindex -mf930
-@opindex -mf934
-These four options select the processor for which the code is optimized.
-These options are deprecated and will be deleted in a future GCC release.
-They have been replaced with @option{-mcpu=xxx}.
-
@item -mcpu=@var{cpu_type}
@opindex mcpu
Set the instruction set, register set, and instruction scheduling parameters
@item -mcmodel=medlow
@opindex mcmodel=medlow
-Generate code for the Medium/Low code model: the program must be linked
-in the low 32 bits of the address space. Pointers are 64 bits.
-Programs can be statically or dynamically linked.
+Generate code for the Medium/Low code model: 64-bit addresses, programs
+must be linked in the low 32 bits of memory. Programs can be statically
+or dynamically linked.
@item -mcmodel=medmid
@opindex mcmodel=medmid
-Generate code for the Medium/Middle code model: the program must be linked
-in the low 44 bits of the address space, the text segment must be less than
-2G bytes, and data segment must be within 2G of the text segment.
-Pointers are 64 bits.
+Generate code for the Medium/Middle code model: 64-bit addresses, programs
+must be linked in the low 44 bits of memory, the text and data segments must
+be less than 2GB in size and the data segment must be located within 2GB of
+the text segment.
@item -mcmodel=medany
@opindex mcmodel=medany
-Generate code for the Medium/Anywhere code model: the program may be linked
-anywhere in the address space, the text segment must be less than
-2G bytes, and data segment must be within 2G of the text segment.
-Pointers are 64 bits.
+Generate code for the Medium/Anywhere code model: 64-bit addresses, programs
+may be linked anywhere in memory, the text and data segments must be less
+than 2GB in size and the data segment must be located within 2GB of the
+text segment.
@item -mcmodel=embmedany
@opindex mcmodel=embmedany
Generate code for the Medium/Anywhere code model for embedded systems:
-assume a 32-bit text and a 32-bit data segment, both starting anywhere
-(determined at link time). Register %g4 points to the base of the
-data segment. Pointers are still 64 bits.
-Programs are statically linked, PIC is not supported.
+64-bit addresses, the text and data segments must be less than 2GB in
+size, both starting anywhere in memory (determined at link time). The
+global register %g4 points to the base of the data segment. Programs
+are statically linked and PIC is not supported.
@item -mstack-bias
@itemx -mno-stack-bias
architectures:
@table @gcctabopt
+@item -mabi=@var{name}
+@opindex mabi
+Generate code for the specified ABI. Permissible values are: @samp{apcs-gnu},
+@samp{atpcs}, @samp{aapcs} and @samp{iwmmxt}.
+
@item -mapcs-frame
@opindex mapcs-frame
Generate a stack frame that is compliant with the ARM Procedure Call
library that comes with GCC, with @option{-msoft-float} in order for
this to work.
+@item -mfloat-abi=@var{name}
+@opindex mfloat-abi
+Specifies which ABI to use for floating point values. Permissible values
+are: @samp{soft}, @samp{softfp} and @samp{hard}.
+
+@samp{soft} and @samp{hard} are equivalent to @option{-msoft-float}
+and @option{-mhard-float} respectively. @samp{softfp} allows the generation
+of floating point instructions, but still uses the soft-float calling
+conventions.
+
@item -mlittle-endian
@opindex mlittle-endian
Generate code for a processor running in little-endian mode. This is
assembly code. This option can be used in conjunction with or instead
of the @option{-mcpu=} option. Permissible names are: @samp{armv2},
@samp{armv2a}, @samp{armv3}, @samp{armv3m}, @samp{armv4}, @samp{armv4t},
-@samp{armv5}, @samp{armv5t}, @samp{armv5te}, @samp{armv6j},
+@samp{armv5}, @samp{armv5t}, @samp{armv5te}, @samp{armv6}, @samp{armv6j},
@samp{iwmmxt}, @samp{ep9312}.
-@item -mfpe=@var{number}
+@item -mfpu=@var{name}
+@itemx -mfpe=@var{number}
@itemx -mfp=@var{number}
+@opindex mfpu
@opindex mfpe
@opindex mfp
-This specifies the version of the floating point emulation available on
-the target. Permissible values are 2 and 3. @option{-mfp=} is a synonym
-for @option{-mfpe=}, for compatibility with older versions of GCC@.
+This specifies what floating point hardware (or hardware emulation) is
+available on the target. Permissible names are: @samp{fpa}, @samp{fpe2},
+@samp{fpe3}, @samp{maverick}, @samp{vfp}. @option{-mfp} and @option{-mfpe}
+are synonyms for @option{-mfpu}=@samp{fpe}@var{number}, for compatibility
+with older versions of GCC@.
+
+If @option{-msoft-float} is specified this specifies the format of
+floating point values.
@item -mstructure-size-boundary=@var{n}
@opindex mstructure-size-boundary
The size of all structures and unions will be rounded up to a multiple
-of the number of bits set by this option. Permissible values are 8 and
-32. The default value varies for different toolchains. For the COFF
-targeted toolchain the default value is 8. Specifying the larger number
-can produce faster, more efficient code, but can also increase the size
-of the program. The two values are potentially incompatible. Code
-compiled with one value cannot necessarily expect to work with code or
-libraries compiled with the other value, if they exchange information
-using structures or unions.
+of the number of bits set by this option. Permissible values are 8, 32
+and 64. The default value varies for different toolchains. For the COFF
+targeted toolchain the default value is 8. A value of 64 is only allowed
+if the underlying ABI supports it.
+
+Specifying the larger number can produce faster, more efficient code, but
+can also increase the size of the program. Different values are potentially
+incompatible. Code compiled with one value cannot necessarily expect to
+work with code or libraries compiled with another value, if they exchange
+information using structures or unions.
@item -mabort-on-noreturn
@opindex mabort-on-noreturn
@samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823},
@samp{860}, @samp{970}, @samp{common}, @samp{ec603e}, @samp{G3},
@samp{G4}, @samp{G5}, @samp{power}, @samp{power2}, @samp{power3},
-@samp{power4}, @samp{powerpc}, @samp{powerpc64}, @samp{rios},
-@samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64a}.
+@samp{power4}, @samp{power5}, @samp{powerpc}, @samp{powerpc64},
+@samp{rios}, @samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64a}.
@option{-mcpu=common} selects a completely generic processor. Code
generated under this option will run on any POWER or PowerPC processor.
@itemx -mno-longcall
@opindex mlongcall
@opindex mno-longcall
-Default to making all function calls via pointers, so that functions
-which reside further than 64 megabytes (67,108,864 bytes) from the
-current location can be called. This setting can be overridden by the
-@code{shortcall} function attribute, or by @code{#pragma longcall(0)}.
+Default to making all function calls indirectly, using a register, so
+that functions which reside further than 32 megabytes (33,554,432
+bytes) from the current location can be called. This setting can be
+overridden by the @code{shortcall} function attribute, or by
+@code{#pragma longcall(0)}.
Some linkers are capable of detecting out-of-range calls and generating
glue code on the fly. On these systems, long calls are unnecessary and
as can the GNU linker for PowerPC/64. It is planned to add this feature
to the GNU linker for 32-bit PowerPC systems as well.
+On Darwin/PPC systems, @code{#pragma longcall} will generate ``jbsr
+callee, L42'', plus a ``branch island'' (glue code). The two target
+addresses represent the callee and the ``branch island.'' The
+Darwin/PPC linker will prefer the first address and generate a ``bl
+callee'' if the PPC ``bl'' instruction will reach the callee directly;
+otherwise, the linker will generate ``bl L42'' to call the ``branch
+island.'' The ``branch island'' is appended to the body of the
+calling function; it computes the full 32-bit address of the callee
+and jumps to it.
+
On Mach-O (Darwin) systems, this option directs the compiler emit to
the glue for every direct call, and the Darwin linker decides whether
to use or discard it.
@samp{rm9000},
@samp{orion},
@samp{sb1},
-@samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4300},
+@samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4130}, @samp{vr4300},
@samp{vr5000}, @samp{vr5400} and @samp{vr5500}.
The special value @samp{from-abi} selects the
most compatible architecture for the selected ABI (that is,
generates 64-bit code when you select a 64-bit architecture, but you
can use @option{-mgp32} to get 32-bit code instead.
+For information about the O64 ABI, see
+@w{@uref{http://gcc.gnu.org/projects/mipso64-abi.html}}.
+
@item -mabicalls
@itemx -mno-abicalls
@opindex mabicalls
addresses. The alternative, selected by @option{-mno-explicit-relocs},
is to use assembler macros instead.
-@option{-mexplicit-relocs} is usually the default if GCC was
-configured to use an assembler that supports relocation operators.
-However, there are two exceptions:
-
-@itemize @bullet
-@item
-GCC is not yet able to generate explicit relocations for the combination
-of @option{-mabi=64} and @option{-mno-abicalls}. This will be addressed
-in a future release.
-
-@item
-The combination of @option{-mabicalls} and @option{-fno-unit-at-a-time}
+@option{-mexplicit-relocs} is usually the default if GCC was configured
+to use an assembler that supports relocation operators. However, the
+combination of @option{-mabicalls} and @option{-fno-unit-at-a-time}
implies @option{-mno-explicit-relocs} unless explicitly overridden.
This is because, when generating abicalls, the choice of relocation
depends on whether a symbol is local or global. In some rare cases,
GCC will not be able to decide this until the whole compilation unit
has been read.
-@end itemize
@item -mrnames
@itemx -mno-rnames
Tell the MIPS assembler to not run its preprocessor over user
assembler files (with a @samp{.s} suffix) when assembling them.
+@item -mfix-r4000
+@itemx -mno-fix-r4000
+@opindex mfix-r4000
+@opindex mno-fix-r4000
+Work around certain R4000 CPU errata:
+@itemize @minus
+@item
+A double-word or a variable shift may give an incorrect result if executed
+immediately after starting an integer division.
+@item
+A double-word or a variable shift may give an incorrect result if executed
+while an integer multiplication is in progress.
+@item
+An integer division may give an incorrect result if started in a delay slot
+of a taken branch or a jump.
+@end itemize
+
+@item -mfix-r4400
+@itemx -mno-fix-r4400
+@opindex mfix-r4400
+@opindex mno-fix-r4400
+Work around certain R4400 CPU errata:
+@itemize @minus
+@item
+A double-word or a variable shift may give an incorrect result if executed
+immediately after starting an integer division.
+@end itemize
+
+@item -mfix-vr4120
+@itemx -mno-fix-vr4120
+@opindex mfix-vr4120
+Work around certain VR4120 errata:
+@itemize @minus
+@item
+@code{dmultu} does not always produce the correct result.
+@item
+@code{div} and @code{ddiv} do not always produce the correct result if one
+of the operands is negative.
+@end itemize
+The workarounds for the division errata rely on special functions in
+@file{libgcc.a}. At present, these functions are only provided by
+the @code{mips64vr*-elf} configurations.
+
+Other VR4120 errata require a nop to be inserted between certain pairs of
+instructions. These errata are handled by the assembler, not by GCC itself.
+
@item -mfix-sb1
@itemx -mno-fix-sb1
@opindex mfix-sb1
arguments as the common @code{_flush_func()}, that is, the address of the
memory range for which the cache is being flushed, the size of the
memory range, and the number 3 (to flush both caches). The default
-depends on the target gcc was configured for, but commonly is either
+depends on the target GCC was configured for, but commonly is either
@samp{_flush_func} or @samp{__cpu_flush}.
@item -mbranch-likely
Intel PentiumPro CPU.
@item pentium2
Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.
-@item pentium3
+@item pentium3, pentium3m
Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set
support.
-@item pentium4
+@item pentium-m
+Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set
+support. Used by Centrino notebooks.
+@item pentium4, pentium4m
Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.
+@item prescott
+Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction
+set support.
+@item nocona
+Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE,
+SSE2 and SSE3 instruction set support.
@item k6
AMD K6 CPU with MMX instruction set support.
@item k6-2, k6-3
@item -mfpmath=@var{unit}
@opindex march
-generate floating point arithmetics for selected unit @var{unit}. the choices
+Generate floating point arithmetics for selected unit @var{unit}. The choices
for @var{unit} are:
@table @samp
@option{-msse2} switches to enable SSE extensions and make this option
effective. For x86-64 compiler, these extensions are enabled by default.
-The resulting code should be considerably faster in majority of cases and avoid
+The resulting code should be considerably faster in the majority of cases and avoid
the numerical instability problems of 387 code, but may break some existing
code that expects temporaries to be 80bit.
-This is the default choice for x86-64 compiler.
-
-@item pni
-Use all SSE extensions enabled by @option{-msse2} as well as the new
-SSE extensions in Prescott New Instructions. @option{-mpni} also
-enables 2 builtin functions, @code{__builtin_ia32_monitor} and
-@code{__builtin_ia32_mwait}, for new instructions @code{monitor} and
-@code{mwait}.
+This is the default choice for the x86-64 compiler.
@item sse,387
Attempt to utilize both instruction sets at once. This effectively double the
amount of available registers and on chips with separate execution units for
387 and SSE the execution resources too. Use this option with care, as it is
-still experimental, because gcc register allocator does not model separate
+still experimental, because the GCC register allocator does not model separate
functional units well resulting in instable performance.
@end table
standard of 80 bits for a @code{long double}.
@strong{Warning:} if you override the default value for your target ABI, the
-structures and arrays containing @code{long double} will change their size as
-well as function calling convention for function taking @code{long double}
-will be modified. Hence they will not be binary compatible with arrays or
-structures in code compiled without that switch.
+structures and arrays containing @code{long double} variables will change
+their size as well as function calling convention for function taking
+@code{long double} will be modified. Hence they will not be binary
+compatible with arrays or structures in code compiled without that switch.
@item -msvr3-shlib
@itemx -mno-sse
@item -msse2
@itemx -mno-sse2
-@item -mpni
-@itemx -mno-pni
+@item -msse3
+@itemx -mno-sse3
@item -m3dnow
@itemx -mno-3dnow
@opindex mmmx
@opindex m3dnow
@opindex mno-3dnow
These switches enable or disable the use of built-in functions that allow
-direct access to the MMX, SSE and 3Dnow extensions of the instruction set.
+direct access to the MMX, SSE, SSE2, SSE3 and 3Dnow extensions of the
+instruction set.
@xref{X86 Built-in Functions}, for details of the functions enabled
and disabled by these switches.
@opindex mno-align-stringops
Do not align destination of inlined string operations. This switch reduces
code size and improves performance in case the destination is already aligned,
-but gcc don't know about it.
+but GCC doesn't know about it.
@item -minline-all-stringops
@opindex minline-all-stringops
explicitly or implicitly, with the GNU linker. This option does not
have any affect on which ld is called, it only changes what parameters
are passed to that ld. The ld that is called is determined by the
-@option{--with-ld} configure option, gcc's program search path, and
+@option{--with-ld} configure option, GCC's program search path, and
finally by the user's @env{PATH}. The linker used by GCC can be printed
using @samp{which `gcc -print-prog-name=ld`}.
implicitly, with the HP linker. This option does not have any affect on
which ld is called, it only changes what parameters are passed to that
ld. The ld that is called is determined by the @option{--with-ld}
-configure option, gcc's program search path, and finally by the user's
+configure option, GCC's program search path, and finally by the user's
@env{PATH}. The linker used by GCC can be printed using @samp{which
`gcc -print-prog-name=ld`}.
+@item -mfdpic
+@opindex mfdpic
+
+Select the FDPIC ABI, that uses function descriptors to represent
+pointers to functions. Without any PIC/PIE-related options, it
+implies @option{-fPIE}. With @option{-fpic} or @option{-fpie}, it
+assumes GOT entries and small data are within a 12-bit range from the
+GOT base address; with @option{-fPIC} or @option{-fPIE}, GOT offsets
+are computed with 32 bits.
+
+@item -minline-plt
+@opindex minline-plt
+
+Enable inlining of PLT entries in function calls to functions that are
+not known to bind locally. It has no effect without @option{-mfdpic}.
+It's enabled by default if optimizing for speed and compiling for
+shared libraries (i.e., @option{-fPIC} or @option{-fpic}), or when an
+optimization option such as @option{-O3} or above is present in the
+command line.
+
+@item -mgprel-ro
+@opindex mgprel-ro
+
+Enable the use of @code{GPREL} relocations in the FDPIC ABI for data
+that is known to be in read-only sections. It's enabled by default,
+except for @option{-fpic} or @option{-fpie}: even though it may help
+make the global offset table smaller, it trades 1 instruction for 4.
+With @option{-fPIC} or @option{-fPIE}, it trades 3 instructions for 4,
+one of which may be shared by multiple symbols, and it avoids the need
+for a GOT entry for the referenced symbol, so it's more likely to be a
+win. If it is not, @option{-mno-gprel-ro} can be used to disable it.
+
+@item -multilib-library-pic
+@opindex multilib-library-pic
+
+Link with the (library, not FD) pic libraries. It's implied by
+@option{-mlibrary-pic}, as well as by @option{-fPIC} and
+@option{-fpic} without @option{-mfdpic}. You should never have to use
+it explicitly.
+
+@item -mlinked-fp
+@opindex mlinked-fp
+
+Follow the EABI requirement of always creating a frame pointer whenever
+a stack frame is allocated. This option is enabled by default and can
+be disabled with @option{-mno-linked-fp}.
+
@item -mlong-calls
@opindex mno-long-calls
Generate code that uses long call sequences. This ensures that a call
linker.
@end table
-@node Intel 960 Options
-@subsection Intel 960 Options
-
-These @samp{-m} options are defined for the Intel 960 implementations:
-
-@table @gcctabopt
-@item -m@var{cpu-type}
-@opindex mka
-@opindex mkb
-@opindex mmc
-@opindex mca
-@opindex mcf
-@opindex msa
-@opindex msb
-Assume the defaults for the machine type @var{cpu-type} for some of
-the other options, including instruction scheduling, floating point
-support, and addressing modes. The choices for @var{cpu-type} are
-@samp{ka}, @samp{kb}, @samp{mc}, @samp{ca}, @samp{cf},
-@samp{sa}, and @samp{sb}.
-The default is
-@samp{kb}.
-
-@item -mnumerics
-@itemx -msoft-float
-@opindex mnumerics
-@opindex msoft-float
-The @option{-mnumerics} option indicates that the processor does support
-floating-point instructions. The @option{-msoft-float} option indicates
-that floating-point support should not be assumed.
-
-@item -mleaf-procedures
-@itemx -mno-leaf-procedures
-@opindex mleaf-procedures
-@opindex mno-leaf-procedures
-Do (or do not) attempt to alter leaf procedures to be callable with the
-@code{bal} instruction as well as @code{call}. This will result in more
-efficient code for explicit calls when the @code{bal} instruction can be
-substituted by the assembler or linker, but less efficient code in other
-cases, such as calls via function pointers, or using a linker that doesn't
-support this optimization.
-
-@item -mtail-call
-@itemx -mno-tail-call
-@opindex mtail-call
-@opindex mno-tail-call
-Do (or do not) make additional attempts (beyond those of the
-machine-independent portions of the compiler) to optimize tail-recursive
-calls into branches. You may not want to do this because the detection of
-cases where this is not valid is not totally complete. The default is
-@option{-mno-tail-call}.
-
-@item -mcomplex-addr
-@itemx -mno-complex-addr
-@opindex mcomplex-addr
-@opindex mno-complex-addr
-Assume (or do not assume) that the use of a complex addressing mode is a
-win on this implementation of the i960. Complex addressing modes may not
-be worthwhile on the K-series, but they definitely are on the C-series.
-The default is currently @option{-mcomplex-addr} for all processors except
-the CB and CC@.
-
-@item -mcode-align
-@itemx -mno-code-align
-@opindex mcode-align
-@opindex mno-code-align
-Align code to 8-byte boundaries for faster fetching (or don't bother).
-Currently turned on by default for C-series implementations only.
-
-@ignore
-@item -mclean-linkage
-@itemx -mno-clean-linkage
-@opindex mclean-linkage
-@opindex mno-clean-linkage
-These options are not fully implemented.
-@end ignore
-
-@item -mic-compat
-@itemx -mic2.0-compat
-@itemx -mic3.0-compat
-@opindex mic-compat
-@opindex mic2.0-compat
-@opindex mic3.0-compat
-Enable compatibility with iC960 v2.0 or v3.0.
-
-@item -masm-compat
-@itemx -mintel-asm
-@opindex masm-compat
-@opindex mintel-asm
-Enable compatibility with the iC960 assembler.
-
-@item -mstrict-align
-@itemx -mno-strict-align
-@opindex mstrict-align
-@opindex mno-strict-align
-Do not permit (do permit) unaligned accesses.
-
-@item -mold-align
-@opindex mold-align
-Enable structure-alignment compatibility with Intel's gcc release version
-1.3 (based on gcc 1.37). This option implies @option{-mstrict-align}.
-
-@item -mlong-double-64
-@opindex mlong-double-64
-Implement type @samp{long double} as 64-bit floating point numbers.
-Without the option @samp{long double} is implemented by 80-bit
-floating point numbers. The only reason we have it because there is
-no 128-bit @samp{long double} support in @samp{fp-bit.c} yet. So it
-is only useful for people using soft-float targets. Otherwise, we
-should recommend against use of it.
-
-@end table
-
@node DEC Alpha Options
@subsection DEC Alpha Options
scheduling, but does not always do so.
@end table
-@node D30V Options
-@subsection D30V Options
-@cindex D30V Options
-
-These @samp{-m} options are defined for D30V implementations:
-
-@table @gcctabopt
-@item -mextmem
-@opindex mextmem
-Link the @samp{.text}, @samp{.data}, @samp{.bss}, @samp{.strings},
-@samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections into external
-memory, which starts at location @code{0x80000000}.
-
-@item -mextmemory
-@opindex mextmemory
-Same as the @option{-mextmem} switch.
-
-@item -monchip
-@opindex monchip
-Link the @samp{.text} section into onchip text memory, which starts at
-location @code{0x0}. Also link @samp{.data}, @samp{.bss},
-@samp{.strings}, @samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections
-into onchip data memory, which starts at location @code{0x20000000}.
-
-@item -mno-asm-optimize
-@itemx -masm-optimize
-@opindex mno-asm-optimize
-@opindex masm-optimize
-Disable (enable) passing @option{-O} to the assembler when optimizing.
-The assembler uses the @option{-O} option to automatically parallelize
-adjacent short instructions where possible.
-
-@item -mbranch-cost=@var{n}
-@opindex mbranch-cost
-Increase the internal costs of branches to @var{n}. Higher costs means
-that the compiler will issue more instructions to avoid doing a branch.
-The default is 2.
-
-@item -mcond-exec=@var{n}
-@opindex mcond-exec
-Specify the maximum number of conditionally executed instructions that
-replace a branch. The default is 4.
-@end table
-
@node S/390 and zSeries Options
@subsection S/390 and zSeries Options
@cindex S/390 and zSeries Options
The options @option{-metrax4} and @option{-metrax100} are synonyms for
@option{-march=v3} and @option{-march=v8} respectively.
+@item -mmul-bug-workaround
+@itemx -mno-mul-bug-workaround
+@opindex mmul-bug-workaround
+@opindex mno-mul-bug-workaround
+Work around a bug in the @code{muls} and @code{mulu} instructions for CPU
+models where it applies. This option is active by default.
+
@item -mpdebug
@opindex mpdebug
Enable CRIS-specific verbose debug-related information in the assembly
@item -mlibrary-pic
@opindex mlibrary-pic
-Enable PIC support for building libraries
+Generate position-independent EABI code.
@item -macc-4
@opindex macc-4
`precompile' a header file; then, if builds can use the precompiled
header file they will be much faster.
+@strong{Caution:} There are a few known situations where GCC will
+crash when trying to use a precompiled header. If you have trouble
+with a precompiled header, you should remove the precompiled header
+and compile without it. In addition, please use GCC's on-line
+defect-tracking system to report any problems you encounter with
+precompiled headers. @xref{Bugs}.
+
To create a precompiled header file, simply compile it as you would any
other file, if necessary using the @option{-x} option to make the driver
treat it as a C or C++ header file. You will probably want to use a
If you need to precompile the same header file for different
languages, targets, or compiler options, you can instead make a
@emph{directory} named like @file{all.h.gch}, and put each precompiled
-header in the directory. (It doesn't matter what you call the files
-in the directory, every precompiled header in the directory will be
-considered.) The first precompiled header encountered in the
-directory that is valid for this compilation will be used; they're
-searched in no particular order.
+header in the directory, perhaps using @option{-o}. It doesn't matter
+what you call the files in the directory, every precompiled header in
+the directory will be considered. The first precompiled header
+encountered in the directory that is valid for this compilation will
+be used; they're searched in no particular order.
There are many other possibilities, limited only by your imagination,
good sense, and the constraints of your build system.
@itemize
@item
Only one precompiled header can be used in a particular compilation.
+
@item
A precompiled header can't be used once the first C token is seen. You
can have preprocessor directives before a precompiled header; you can
even include a precompiled header from inside another header, so long as
there are no C tokens before the @code{#include}.
+
@item
The precompiled header file must be produced for the same language as
the current compilation. You can't use a C precompiled header for a C++
compilation.
+
@item
The precompiled header file must be produced by the same compiler
version and configuration as the current compilation is using.
The easiest way to guarantee this is to use the same compiler binary
for creating and using precompiled headers.
+
@item
-Any macros defined before the precompiled header (including with
-@option{-D}) must either be defined in the same way as when the
-precompiled header was generated, or must not affect the precompiled
-header, which usually means that the they don't appear in the
-precompiled header at all.
+Any macros defined before the precompiled header is included must
+either be defined in the same way as when the precompiled header was
+generated, or must not affect the precompiled header, which usually
+means that the they don't appear in the precompiled header at all.
+
+The @option{-D} option is one way to define a macro before a
+precompiled header is included; using a @code{#define} can also do it.
+There are also some options that define macros implicitly, like
+@option{-O} and @option{-Wdeprecated}; the same rule applies to macros
+defined this way.
+
+@item If debugging information is output when using the precompiled
+header, using @option{-g} or similar, the same kind of debugging information
+must have been output when building the precompiled header. However,
+a precompiled header built using @option{-g} can be used in a compilation
+when no debugging information is being output.
+
+@item The same @option{-m} options must generally be used when building
+and using the precompiled header. @xref{Submodel Options},
+for any cases where this rule is relaxed.
+
+@item Each of the following options must be the same when building and using
+the precompiled header:
+
+@gccoptlist{-fexceptions -funit-at-a-time}
+
@item
-Certain command-line options must be defined in the same way as when the
-precompiled header was generated. At present, it's not clear which
-options are safe to change and which are not; the safest choice is to
-use exactly the same options when generating and using the precompiled
-header.
+Some other command-line options starting with @option{-f},
+@option{-p}, or @option{-O} must be defined in the same way as when
+the precompiled header was generated. At present, it's not clear
+which options are safe to change and which are not; the safest choice
+is to use exactly the same options when generating and using the
+precompiled header. The following are known to be safe:
+
+@gccoptlist{-pedantic-errors}
+
@end itemize
-For all of these but the last, the compiler will automatically ignore
-the precompiled header if the conditions aren't met. For the last item,
-some option changes will cause the precompiled header to be rejected,
-but not all incompatible option combinations have yet been found. If
-you find a new incompatible combination, please consider filing a bug
-report, see @ref{Bugs}.
+For all of these except the last, the compiler will automatically
+ignore the precompiled header if the conditions aren't met. If you
+find an option combination that doesn't work and doesn't cause the
+precompiled header to be ignored, please consider filing a bug report,
+see @ref{Bugs}.
@node Running Protoize
@section Running Protoize
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