PR c/16833

	* doc/extend.texi, doc/invoke.texi: Document interaction of
	-fno-builtin with format checks.  Note that built-in functions
	have effects beyond generating code that avoids calls to those
	functions.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@87957 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 93ad667..3c44c68 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2004-09-23  Joseph S. Myers  <jsm@polyomino.org.uk>
+
+       PR c/16833
+       * doc/extend.texi, doc/invoke.texi: Document interaction of
+       -fno-builtin with format checks.  Note that built-in functions
+       have effects beyond generating code that avoids calls to those
+       functions.
+

 2004-09-23  Frank Ch. Eigler <fche@redhat.com>
 
        PR tree-optimization/17533
 2004-09-23  Frank Ch. Eigler <fche@redhat.com>
 
        PR tree-optimization/17533

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index af5b9d1..a407663 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -1764,10 +1764,11 @@ start with the third argument, so the correct parameters for the format
 attribute are 2 and 3.
 
 @opindex ffreestanding
 attribute are 2 and 3.
 
 @opindex ffreestanding

+@opindex fno-builtin

 The @code{format} attribute allows you to identify your own functions
 which take format strings as arguments, so that GCC can check the
 calls to these functions for errors.  The compiler always (unless
 The @code{format} attribute allows you to identify your own functions
 which take format strings as arguments, so that GCC can check the
 calls to these functions for errors.  The compiler always (unless

-@option{-ffreestanding} is used) checks formats
+@option{-ffreestanding} or @option{-fno-builtin} is used) checks formats

 for the standard library functions @code{printf}, @code{fprintf},
 @code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime},
 @code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such
 for the standard library functions @code{printf}, @code{fprintf},
 @code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime},
 @code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such


@@ -1824,7 +1825,8 @@ type function whose operands are a call to one of your own function.
 The compiler always treats @code{gettext}, @code{dgettext}, and
 @code{dcgettext} in this manner except when strict ISO C support is
 requested by @option{-ansi} or an appropriate @option{-std} option, or
 The compiler always treats @code{gettext}, @code{dgettext}, and
 @code{dcgettext} in this manner except when strict ISO C support is
 requested by @option{-ansi} or an appropriate @option{-std} option, or

-@option{-ffreestanding} is used.  @xref{C Dialect Options,,Options
+@option{-ffreestanding} or @option{-fno-builtin}
+is used.  @xref{C Dialect Options,,Options

 Controlling C Dialect}.
 
 @item function_vector
 Controlling C Dialect}.
 
 @item function_vector

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index fae3018..e86677d 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1173,7 +1173,14 @@ instructions that adjust the stack directly, and calls to @code{memcpy}
 may become inline copy loops.  The resulting code is often both smaller
 and faster, but since the function calls no longer appear as such, you
 cannot set a breakpoint on those calls, nor can you change the behavior
 may become inline copy loops.  The resulting code is often both smaller
 and faster, but since the function calls no longer appear as such, you
 cannot set a breakpoint on those calls, nor can you change the behavior

-of the functions by linking with a different library.
+of the functions by linking with a different library.  In addition,
+when a function is recognized as a built-in function, GCC may use
+information about that function to warn about problems with calls to
+that function, or to generate more efficient code, even if the
+resulting code still contains calls to that function.  For example,
+warnings are given with @option{-Wformat} for bad calls to
+@code{printf}, when @code{printf} is built in, and @code{strlen} is
+known not to modify global memory.

 
 With the @option{-fno-builtin-@var{function}} option
 only the built-in function @var{function} is
 
 With the @option{-fno-builtin-@var{function}} option
 only the built-in function @var{function} is


@@ -2161,6 +2168,8 @@ messages.
 
 @item -Wformat
 @opindex Wformat
 
 @item -Wformat
 @opindex Wformat

+@opindex ffreestanding
+@opindex fno-builtin

 Check calls to @code{printf} and @code{scanf}, etc., to make sure that
 the arguments supplied have types appropriate to the format string
 specified, and that the conversions specified in the format string make
 Check calls to @code{printf} and @code{scanf}, etc., to make sure that
 the arguments supplied have types appropriate to the format string
 specified, and that the conversions specified in the format string make


@@ -2168,6 +2177,10 @@ sense.  This includes standard functions, and others specified by format
 attributes (@pxref{Function Attributes}), in the @code{printf},
 @code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension,
 not in the C standard) families (or other target-specific families).
 attributes (@pxref{Function Attributes}), in the @code{printf},
 @code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension,
 not in the C standard) families (or other target-specific families).

+Which functions are checked without format attributes having been
+specified depends on the standard version selected, and such checks of
+functions without the attribute specified are disabled by
+@option{-ffreestanding} or @option{-fno-builtin}.

 
 The formats are checked against the format features supported by GNU
 libc version 2.2.  These include all ISO C90 and C99 features, as well
 
 The formats are checked against the format features supported by GNU
 libc version 2.2.  These include all ISO C90 and C99 features, as well