@xref{C Dialect Options,,Options Controlling C Dialect}.
@gccoptlist{-ansi -std=@var{standard} -aux-info @var{filename} @gol
-fno-asm -fno-builtin -fno-builtin-@var{function} @gol
--fhosted -ffreestanding -fms-extensions @gol
+-fhosted -ffreestanding -fopenmp -fms-extensions @gol
-trigraphs -no-integrated-cpp -traditional -traditional-cpp @gol
-fallow-single-precision -fcond-mismatch @gol
-fsigned-bitfields -fsigned-char @gol
-Wmain -Wmissing-braces -Wmissing-field-initializers @gol
-Wmissing-format-attribute -Wmissing-include-dirs @gol
-Wmissing-noreturn @gol
--Wno-multichar -Wnonnull -Woverlength-strings -Wpacked -Wpadded @gol
+-Wno-multichar -Wnonnull -Wno-overflow @gol
+-Woverlength-strings -Wpacked -Wpadded @gol
-Wparentheses -Wpointer-arith -Wno-pointer-to-int-cast @gol
-Wredundant-decls @gol
-Wreturn-type -Wsequence-point -Wshadow @gol
-fsched-spec-load-dangerous @gol
-fsched-stalled-insns=@var{n} -fsched-stalled-insns-dep=@var{n} @gol
-fsched2-use-superblocks @gol
--fsched2-use-traces -freschedule-modulo-scheduled-loops @gol
+-fsched2-use-traces -fsee -freschedule-modulo-scheduled-loops @gol
-fsection-anchors -fsignaling-nans -fsingle-precision-constant @gol
-fstack-protector -fstack-protector-all @gol
-fstrict-aliasing -ftracer -fthread-jumps @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 -msse3 -m3dnow -msselibm @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} -msseregparm @gol
+-mstackrealign @gol
-momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol
-mcmodel=@var{code-model} @gol
-m32 -m64 -mlarge-data-threshold=@var{num}}
-fargument-noalias-global -fargument-noalias-anything
-fleading-underscore -ftls-model=@var{model} @gol
-ftrapv -fwrapv -fbounds-check @gol
--fvisibility -fopenmp}
+-fvisibility}
@end table
@menu
@xref{Standards,,Language Standards Supported by GCC}, for details of
freestanding and hosted environments.
+@item -fopenmp
+@opindex fopenmp
+@cindex openmp parallel
+Enable handling of OpenMP directives @code{#pragma omp} in C/C++ and
+@code{!$omp} in Fortran. When @option{-fopenmp} is specified, the
+compiler generates parallel code according to the OpenMP Application
+Program Interface v2.5 @w{@uref{http://www.openmp.org/}}.
+
@item -fms-extensions
@opindex fms-extensions
Accept some non-standard constructs used in Microsoft header files.
on load and link times of a DSO as it massively reduces the size of the
dynamic export table when the library makes heavy use of templates.
-The behaviour of this switch is not quite the same as marking the
-methods as hidden directly. Normally if there is a class with default
-visibility which has a hidden method, the effect of this is that the
-method must be defined in only one shared object. This switch does
-not have this restriction.
-
You may mark a method as having a visibility explicitly to negate the
effect of the switch for that method. For example, if you do want to
-compare pointers to a particular inline method, you might mark it as
-having default visibility.
+compare pointers to a particular inline method, or the method has
+local static data, you might mark it as having default visibility.
@item -fno-weak
@opindex fno-weak
been applied. For instance @code{\u207F}, ``SUPERSCRIPT LATIN SMALL
LETTER N'', will display just like a regular @code{n} which has been
placed in a superscript. ISO 10646 defines the @dfn{NFKC}
-normalisation scheme to convert all these into a standard form as
+normalization scheme to convert all these into a standard form as
well, and GCC will warn if your code is not in NFKC if you use
@option{-Wnormalized=nfkc}. This warning is comparable to warning
about every identifier that contains the letter O because it might be
(@pxref{Function Attributes}, @pxref{Variable Attributes},
@pxref{Type Attributes}.)
+@item -Wno-overflow
+@opindex Wno-overflow
+Do not warn about compile-time overflow in constant expressions.
+
@item -Wpacked
@opindex Wpacked
Warn if a structure is given the packed attribute, but the packed
and possibly the ability to debug the program.
The compiler performs optimization based on the knowledge it has of
-the program. Optimization levels @option{-O2} and above, in
+the program. Optimization levels @option{-O} and above, in
particular, enable @emph{unit-at-a-time} mode, which allows the
compiler to consider information gained from later functions in
the file when compiling a function. Compiling multiple files at
-ftree-copyrename @gol
-ftree-fre @gol
-ftree-ch @gol
+-funit-at-a-time @gol
-fmerge-constants}
@option{-O} also turns on @option{-fomit-frame-pointer} on machines
-fstrict-aliasing @gol
-fdelete-null-pointer-checks @gol
-freorder-blocks -freorder-functions @gol
--funit-at-a-time @gol
-falign-functions -falign-jumps @gol
-falign-loops -falign-labels @gol
-ftree-vrp @gol
sense when scheduling after register allocation, i.e.@: with
@option{-fschedule-insns2} or at @option{-O2} or higher.
+@item -fsee
+@opindex fsee
+Eliminates redundant extension instructions and move the non redundant
+ones to optimal placement using LCM.
+
@item -freschedule-modulo-scheduled-loops
@opindex fscheduling-in-modulo-scheduled-loops
The modulo scheduling comes before the traditional scheduling, if a loop was modulo scheduled
As a temporary workaround, @option{-fno-unit-at-a-time} can be used,
but this scheme may not be supported by future releases of GCC@.
-Enabled at levels @option{-O2}, @option{-O3}.
+Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
@item -fno-toplevel-reorder
Do not reorder top-level functions, variables, and @code{asm}
compile time increase with probably slightly better performance. The default
value is 100.
-@item max-cselib-memory-location
+@item max-cselib-memory-locations
The maximum number of memory locations cselib should take into acount.
Increasing values mean more aggressive optimization, making the compile time
increase with probably slightly better performance. The default value is 500.
-@item max-flow-memory-location
-Similar as @option{max-cselib-memory-location} but for dataflow liveness.
+@item max-flow-memory-locations
+Similar as @option{max-cselib-memory-locations} but for dataflow liveness.
The default value is 100.
@item reorder-blocks-duplicate
The maximum number of iterations through CFG to extend regions.
0 - disable region extension,
N - do at most N iterations.
-The default value is 2.
+The default value is 0.
@item max-sched-insn-conflict-delay
The maximum conflict delay for an insn to be considered for speculative motion.
generic instruction set applicable to all processors. In contrast,
@option{-mtune} indicates the processor (or, in this case, collection of
processors) for which the code is optimized.
+@item native
+This selects the CPU to tune for at compilation time by determining
+the processor type of the compiling machine. Using @option{-mtune=native}
+will produce code optimized for the local machine under the constraints
+of the selected instruction set. Using @option{-march=native} will
+enable all instruction subsets supported by the local machine (hence
+the result might not run on different machines).
@item i386
Original Intel's i386 CPU@.
@item i486
modules with the same value, including any libraries. This includes
the system libraries and startup modules.
+@item -mstackrealign
+@opindex mstackrealign
+Realign the stack at entry. On the Intel x86, the
+@option{-mstackrealign} option will generate an alternate prologue and
+epilogue that realigns the runtime stack. This supports mixing legacy
+codes that keep a 4-byte aligned stack with modern codes that keep a
+16-byte stack for SSE compatibility. The alternate prologue and
+epilogue are slower and bigger than the regular ones, and the
+alternate prologue requires an extra scratch register; this lowers the
+number of registers available if used in conjunction with the
+@code{regparm} attribute. The @option{-mstackrealign} option is
+incompatible with the nested function prologue; this is considered a
+hard error. See also the attribute @code{force_align_arg_pointer},
+applicable to individual functions.
+
@item -mpreferred-stack-boundary=@var{num}
@opindex mpreferred-stack-boundary
Attempt to keep the stack boundary aligned to a 2 raised to @var{num}
the file containing the CPU detection code should be compiled without
these options.
-@item -msselibm
-@opindex msselibm
-Use special versions of certain libm routines that come with an SSE
-ABI and an SSE implementation. Useful together with @option{-mfpmath=sse}
-to avoid moving values between SSE registers and the x87 FP stack.
-
@item -mpush-args
@itemx -mno-push-args
@opindex mpush-args
@samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823},
@samp{860}, @samp{970}, @samp{8540}, @samp{ec603e}, @samp{G3},
@samp{G4}, @samp{G5}, @samp{power}, @samp{power2}, @samp{power3},
-@samp{power4}, @samp{power5}, @samp{power5+},
+@samp{power4}, @samp{power5}, @samp{power5+}, @samp{power6},
@samp{common}, @samp{powerpc}, @samp{powerpc64},
@samp{rios}, @samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64}.
may need to explicitly say @samp{#pragma GCC visibility push(default)}
before including any such headers.
+@samp{extern} declarations are not affected by @samp{-fvisibility}, so
+a lot of code can be recompiled with @samp{-fvisibility=hidden} with
+no modifications. However, this means that calls to @samp{extern}
+functions with no explicit visibility will use the PLT, so it is more
+effective to use @samp{__attribute ((visibility))} and/or
+@samp{#pragma GCC visibility} to tell the compiler which @samp{extern}
+declarations should be treated as hidden.
+
+Note that @samp{-fvisibility} does affect C++ vague linkage
+entities. This means that, for instance, an exception class that will
+be thrown between DSOs must be explicitly marked with default
+visibility so that the @samp{type_info} nodes will be unified between
+the DSOs.
+
An overview of these techniques, their benefits and how to use them
is at @w{@uref{http://gcc.gnu.org/wiki/Visibility}}.
-@item -fopenmp
-@opindex fopenmp
-@cindex openmp parallel
-Enable handling of OpenMP directives @code{#pragma omp} in C/C++ and
-@code{!$omp} in Fortran. When @option{-fopenmp} is specified, the
-compiler generates parallel code according to the OpenMP Application
-Program Interface v2.5 @w{@uref{http://www.openmp.org/}}.
-
@end table
@c man end
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