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/* Erase sensitive data from memory.
Copyright 2022-2024 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include <string.h>
/* Set S's bytes to C, where S has LEN bytes. The compiler will not
optimize effects away, even if S is dead after the call. */
void *
memset_explicit (void *s, int c, size_t len)
{
#if HAVE_EXPLICIT_MEMSET
return explicit_memset (s, c, len);
#elif HAVE_MEMSET_S
# if !HAVE_MEMSET_S_SUPPORTS_ZERO
if (len > 0)
# endif
(void) memset_s (s, len, c, len);
return s;
#elif defined __GNUC__ && !defined __clang__
memset (s, c, len);
/* Compiler barrier. */
__asm__ volatile ("" ::: "memory");
return s;
#elif defined __clang__
memset (s, c, len);
/* Compiler barrier. */
/* With asm ("" ::: "memory") LLVM analyzes uses of 's' and finds that the
whole thing is dead and eliminates it. Use 'g' to work around this
problem. See <https://bugs.llvm.org/show_bug.cgi?id=15495#c11>. */
__asm__ volatile ("" : : "g"(s) : "memory");
return s;
#else
/* Invoke memset through a volatile function pointer. This defeats compiler
optimizations. */
void * (* const volatile volatile_memset) (void *, int, size_t) = memset;
return volatile_memset (s, c, len);
#endif
}
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