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author | Paul Eggert <eggert@cs.ucla.edu> | 2021-08-01 17:35:17 -0700 |
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committer | Paul Eggert <eggert@cs.ucla.edu> | 2021-08-01 18:06:54 -0700 |
commit | 8c6a99453e4a38fe6b602718e7b5e68444870e07 (patch) | |
tree | d235169d6871faf9d8647a57c5e6cd701d33f9bd /lib | |
parent | b279b399553d273317a7faa59c3ebbfba0c353cd (diff) | |
download | gnulib-8c6a99453e4a38fe6b602718e7b5e68444870e07.tar.gz |
malloca: improve -fanalyzer malloc checking
Diffstat (limited to 'lib')
-rw-r--r-- | lib/malloca.c | 18 | ||||
-rw-r--r-- | lib/malloca.h | 5 |
2 files changed, 16 insertions, 7 deletions
diff --git a/lib/malloca.c b/lib/malloca.c index d7ad095b5a..b4884234a2 100644 --- a/lib/malloca.c +++ b/lib/malloca.c @@ -47,7 +47,8 @@ mmalloca (size_t n) #if HAVE_ALLOCA /* Allocate one more word, used to determine the address to pass to freea(), and room for the alignment ≡ sa_alignment_max mod 2*sa_alignment_max. */ - int plus = sizeof (small_t) + 2 * sa_alignment_max - 1; + uintptr_t alignment2_mask = 2 * sa_alignment_max - 1; + int plus = sizeof (small_t) + alignment2_mask; idx_t nplus; if (!INT_ADD_WRAPV (n, plus, &nplus) && !xalloc_oversized (nplus, 1)) { @@ -55,16 +56,21 @@ mmalloca (size_t n) if (mem != NULL) { - char *p = - (char *)((((uintptr_t)mem + sizeof (small_t) + sa_alignment_max - 1) - & ~(uintptr_t)(2 * sa_alignment_max - 1)) - + sa_alignment_max); + uintptr_t umem = (uintptr_t)mem, umemplus; + /* The INT_ADD_WRAPV avoids signed integer overflow on + theoretical platforms where UINTPTR_MAX <= INT_MAX. */ + INT_ADD_WRAPV (umem, sizeof (small_t) + sa_alignment_max - 1, + &umemplus); + idx_t offset = ((umemplus & ~alignment2_mask) + + sa_alignment_max - umem); + void *vp = mem + offset; + small_t *p = vp; /* Here p >= mem + sizeof (small_t), and p <= mem + sizeof (small_t) + 2 * sa_alignment_max - 1 hence p + n <= mem + nplus. So, the memory range [p, p+n) lies in the allocated memory range [mem, mem + nplus). */ - ((small_t *) p)[-1] = p - mem; + p[-1] = offset; /* p ≡ sa_alignment_max mod 2*sa_alignment_max. */ return p; } diff --git a/lib/malloca.h b/lib/malloca.h index 6fa1d8b205..dbbec3f065 100644 --- a/lib/malloca.h +++ b/lib/malloca.h @@ -65,7 +65,6 @@ extern "C" { # define malloca(N) \ mmalloca (N) #endif -extern void * mmalloca (size_t n); /* Free a block of memory allocated through malloca(). */ #if HAVE_ALLOCA @@ -74,6 +73,10 @@ extern void freea (void *p); # define freea free #endif +extern void *mmalloca (size_t n) + _GL_ATTRIBUTE_MALLOC _GL_ATTRIBUTE_DEALLOC (freea, 1) + _GL_ATTRIBUTE_ALLOC_SIZE ((1)); + /* nmalloca(N,S) is an overflow-safe variant of malloca (N * S). It allocates an array of N objects, each with S bytes of memory, on the stack. N and S should be nonnegative and free of side effects. |