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gmem: Replace SIZE_OVERFLOWS with g_size_checked_mul

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Using the builtin multiplication checks leads to less instructions used
for these common functions (true for clang as well as gcc on x86_64).

Also, from a C perspective, the result is re-used, making code audits
easier.
This commit is contained in:
Tobias Stoeckmann
2025-09-05 22:37:10 +02:00
parent 723c28e116
commit ceb5ac4925
1 changed files with 25 additions and 17 deletions
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42
glib/gmem.c
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@@ -381,8 +381,6 @@ g_try_realloc (gpointer mem,
} }
#define SIZE_OVERFLOWS(a,b) (G_UNLIKELY ((b) > 0 && (a) > G_MAXSIZE / (b)))
/** /**
* g_malloc_n: * g_malloc_n:
* @n_blocks: the number of blocks to allocate * @n_blocks: the number of blocks to allocate
@@ -401,13 +399,15 @@ gpointer
g_malloc_n (gsize n_blocks, g_malloc_n (gsize n_blocks,
gsize n_block_bytes) gsize n_block_bytes)
{ {
if (SIZE_OVERFLOWS (n_blocks, n_block_bytes)) size_t len;
if (!g_size_checked_mul (&len, n_blocks, n_block_bytes))
{ {
g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes", g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
G_STRLOC, n_blocks, n_block_bytes); G_STRLOC, n_blocks, n_block_bytes);
} }
return g_malloc (n_blocks * n_block_bytes); return g_malloc (len);
} }
/** /**
@@ -428,13 +428,15 @@ gpointer
g_malloc0_n (gsize n_blocks, g_malloc0_n (gsize n_blocks,
gsize n_block_bytes) gsize n_block_bytes)
{ {
if (SIZE_OVERFLOWS (n_blocks, n_block_bytes)) size_t len;
if (!g_size_checked_mul (&len, n_blocks, n_block_bytes))
{ {
g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes", g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
G_STRLOC, n_blocks, n_block_bytes); G_STRLOC, n_blocks, n_block_bytes);
} }
return g_malloc0 (n_blocks * n_block_bytes); return g_malloc0 (len);
} }
/** /**
@@ -457,13 +459,15 @@ g_realloc_n (gpointer mem,
gsize n_blocks, gsize n_blocks,
gsize n_block_bytes) gsize n_block_bytes)
{ {
if (SIZE_OVERFLOWS (n_blocks, n_block_bytes)) size_t len;
if (!g_size_checked_mul (&len, n_blocks, n_block_bytes))
{ {
g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes", g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
G_STRLOC, n_blocks, n_block_bytes); G_STRLOC, n_blocks, n_block_bytes);
} }
return g_realloc (mem, n_blocks * n_block_bytes); return g_realloc (mem, len);
} }
/** /**
@@ -481,10 +485,12 @@ gpointer
g_try_malloc_n (gsize n_blocks, g_try_malloc_n (gsize n_blocks,
gsize n_block_bytes) gsize n_block_bytes)
{ {
if (SIZE_OVERFLOWS (n_blocks, n_block_bytes)) size_t len;
if (!g_size_checked_mul (&len, n_blocks, n_block_bytes))
return NULL; return NULL;
return g_try_malloc (n_blocks * n_block_bytes); return g_try_malloc (len);
} }
/** /**
@@ -502,10 +508,12 @@ gpointer
g_try_malloc0_n (gsize n_blocks, g_try_malloc0_n (gsize n_blocks,
gsize n_block_bytes) gsize n_block_bytes)
{ {
if (SIZE_OVERFLOWS (n_blocks, n_block_bytes)) size_t len;
if (!g_size_checked_mul (&len, n_blocks, n_block_bytes))
return NULL; return NULL;
return g_try_malloc0 (n_blocks * n_block_bytes); return g_try_malloc0 (len);
} }
/** /**
@@ -525,10 +533,12 @@ g_try_realloc_n (gpointer mem,
gsize n_blocks, gsize n_blocks,
gsize n_block_bytes) gsize n_block_bytes)
{ {
if (SIZE_OVERFLOWS (n_blocks, n_block_bytes)) size_t len;
if (!g_size_checked_mul (&len, n_blocks, n_block_bytes))
return NULL; return NULL;
return g_try_realloc (mem, n_blocks * n_block_bytes); return g_try_realloc (mem, len);
} }
/** /**
@@ -637,14 +647,12 @@ g_aligned_alloc (gsize n_blocks,
G_STRLOC, alignment, sizeof (void *)); G_STRLOC, alignment, sizeof (void *));
} }
if (SIZE_OVERFLOWS (n_blocks, n_block_bytes)) if (!g_size_checked_mul (&real_size, n_blocks, n_block_bytes))
{ {
g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes", g_error ("%s: overflow allocating %"G_GSIZE_FORMAT"*%"G_GSIZE_FORMAT" bytes",
G_STRLOC, n_blocks, n_block_bytes); G_STRLOC, n_blocks, n_block_bytes);
} }
real_size = n_blocks * n_block_bytes;
if (G_UNLIKELY (real_size == 0)) if (G_UNLIKELY (real_size == 0))
{ {
TRACE (GLIB_MEM_ALLOC ((void *) NULL, real_size, 0, 0)); TRACE (GLIB_MEM_ALLOC ((void *) NULL, real_size, 0, 0));