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From: Siddhesh Poyarekar <siddhesh@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-4978] tree-optimization/105043: Object Size Checking docs cleanup Date: Tue, 3 Jan 2023 15:25:00 +0000 (GMT) [thread overview] Message-ID: <20230103152500.1887F3858D1E@sourceware.org> (raw) https://gcc.gnu.org/g:b3009222b7bb26654c1e93d34e65e8f80ae20595 commit r13-4978-gb3009222b7bb26654c1e93d34e65e8f80ae20595 Author: Siddhesh Poyarekar <siddhesh@gotplt.org> Date: Thu Dec 15 14:24:55 2022 -0500 tree-optimization/105043: Object Size Checking docs cleanup Break the _FORTIFY_SOURCE-specific builtins out into a separate subsection from Object Size Checking built-ins and mention _FORTIFY_SOURCE in there so that the link between the object size checking builtins, the helper builtins (e.g. __builtin___memcpy_chk) and _FORTIFY_SOURCE is clearer. gcc/ChangeLog: PR tree-optimization/105043 * doc/extend.texi (Object Size Checking): Split out into two subsections and mention _FORTIFY_SOURCE. Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org> Diff: --- gcc/doc/extend.texi | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index adba057c190..68d7760bd0c 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -12796,7 +12796,9 @@ __atomic_store_n(&lockvar, 0, __ATOMIC_RELEASE|__ATOMIC_HLE_RELEASE); @end smallexample @node Object Size Checking -@section Object Size Checking Built-in Functions +@section Object Size Checking + +@subsection Object Size Checking Built-in Functions @findex __builtin_object_size @findex __builtin_dynamic_object_size @findex __builtin___memcpy_chk @@ -12878,11 +12880,17 @@ which objects @var{ptr} points to at compile time are the same as in the case of @code{__builtin_object_size}. @end deftypefn -There are built-in functions added for many common string operation -functions, e.g., for @code{memcpy} @code{__builtin___memcpy_chk} -built-in is provided. This built-in has an additional last argument, -which is the number of bytes remaining in the object the @var{dest} -argument points to or @code{(size_t) -1} if the size is not known. +@subsection Object Size Checking and Source Fortification + +Hardening of function calls using the @code{_FORTIFY_SOURCE} macro is +one of the key uses of the object size checking built-in functions. To +make implementation of these features more convenient and improve +optimization and diagnostics, there are built-in functions added for +many common string operation functions, e.g., for @code{memcpy} +@code{__builtin___memcpy_chk} built-in is provided. This built-in has +an additional last argument, which is the number of bytes remaining in +the object the @var{dest} argument points to or @code{(size_t) -1} if +the size is not known. The built-in functions are optimized into the normal string functions like @code{memcpy} if the last argument is @code{(size_t) -1} or if
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