glibc.git/include/string.h, branch master

string: Check if attribute can declared after function declaration

2025-11-10T11:57:56+00:00

Some symbols that might be auto-generated by the compiler are redefined
to internal alias (for instance mempcpy to __mempcpy).  However, if fortify
is enabled, the fortify wrapper is define before the alias re-defined and
clang warns attribute declaration must precede definition.

Use an asm alias if compiler does not support it, instead of an
attribute.

Reviewed-by: H.J. Lu

Implement C23 memset_explicit (bug 32378)

2025-10-01T15:14:09+00:00

Add the C23 memset_explicit function to glibc.  Everything here is
closely based on the approach taken for explicit_bzero.  This includes
the bits that relate to internal uses of explicit_bzero within glibc
(although we don't currently have any such internal uses of
memset_explicit), and also includes the nonnull attribute (when we
move to nonnull_if_nonzero for various functions following C2y, this
function should be included in that change).

The function is declared both for __USE_MISC and for __GLIBC_USE (ISOC23)
(so by default not just for compilers defaulting to C23 mode).

Tested for x86_64 and x86.

include/string.h: Also redirect calls if not inlined in libpthread

2025-01-07T19:53:18+00:00

htl's pt-alloc.c calls __mempcpy, which is #defined to
__builtin_mempcpy, but which does not happen to get inlined (the size is
dynamic), and then gcc emits a reference to mempcpy, thus violating
symbol exposition standard. We thus also have to redirect such
references to __mempcpy too.

Redirect mempcpy and stpcpy only in libc.a

2025-01-02T21:30:44+00:00

The mempcpy and stpcpy redirections to __mempcpy and __stpcpy were added
by

commit 939da41143341bbcdd3dd50ee7b57776603da260
Author: Joseph Myers 
Date:   Wed Nov 12 22:36:34 2014 +0000

    Fix stpcpy / mempcpy namespace (bug 17573).

to fix the namespace bug since __mempcpy and __stpcpy were defined as
macros in .  These macros call __builtin_mempcpy and
__builtin_stpcpy which may end up calling the C functions mempcpy
and stpcpy.  In libc.so, libc_hidden_builtin_proto ensures that calls
to mempcpy and stpcpy are in turn mapped to call __GI_mempcpy and
__GI_stpcpy.  The redirections were applied outside of libc.so, including
libc.a, to map mempcpy and stpcpy to __mempcpy and __stpcpy.  Since

commit 18b10de7ced9e9c3843299fb600e40b11af3e0af
Author: Wilco Dijkstra 
Date:   Mon Jun 12 15:19:38 2017 +0100

    2017-06-12  Wilco Dijkstra  

    There is no longer a need for string2.h, so remove it and all mention of it.
    Move the redirect for __stpcpy to include/string.h since it is
still required
    until all internal uses have been renamed.
    This fixes several linknamespace/localplt failures when building with -Os.

removed the __mempcpy and __stpcpy macros from the public header file,
limit these redirections to libc.a to avoid Clang error:

In file included from tst-iconv-sticky-input-error.c:22:
In file included from ./gconv_int.h:24:
../include/string.h:182:44: error: attribute declaration must precede definition [-Werror,-Wignored-attributes]
  182 | extern __typeof (mempcpy) mempcpy __asm__ ("__mempcpy");
      |                                            ^
../string/bits/string_fortified.h:42:8: note: previous definition is here
   42 | __NTH (mempcpy (void *__restrict __dest, const void *__restrict __src,
      |        ^

when testing with Clang for fortify build.

Signed-off-by: H.J. Lu 
Reviewed-by: Sam James

string: Add hidden builtin definition for __strcpy_chk.

2024-02-06T08:17:04+00:00

Otherwise on at least x86_64 and s390x there is an unwanted PLT entry
in libc.so when configured with --enable-fortify-source=3 and build
with -Os.

This is observed in elf/check-localplt
Extra PLT reference: libc.so: __strcpy_chk

The call to PLT entry is in inet/ruserpass.c.
Reviewed-by: Adhemerval Zanella

chk: Add and fix hidden builtin definitions for *_chk

2023-08-03T20:46:48+00:00

Otherwise on gnu-i686 there are unwanted PLT entries in libc.so when
fortification is enabled.

Tested for i686-gnu, x86_64-gnu, i686-linux-gnu and x86_64-linux-gnu

string: Ensure *_chk routines have their hidden builtin definition available

2023-07-05T14:59:48+00:00

If libc_hidden_builtin_{def,proto} isn't properly set for *_chk routines,
there are unwanted PLT entries in libc.so.

Reviewed-by: Siddhesh Poyarekar

Implement strlcpy and strlcat [BZ #178]

2023-06-14T16:10:08+00:00

These functions are about to be added to POSIX, under Austin Group
issue 986.

The fortified strlcat implementation does not raise SIGABRT if the
destination buffer does not contain a null terminator, it just
inherits the non-failing regular strlcat behavior.

Reviewed-by: Siddhesh Poyarekar

string: Remove string_private.h

2023-02-17T18:56:54+00:00

Now that _STRING_ARCH_unaligned is not used anymore.

Reviewed-by: Wilco Dijkstra

string: Add libc_hidden_proto for memrchr

2023-02-08T20:13:58+00:00

Although static linker can optimize it to local call, it follows the
internal scheme to provide hidden proto and definitions.

Reviewed-by: Carlos Eduardo Seo