77 lines
1.9 KiB
C
77 lines
1.9 KiB
C
/* Fail-proof memory allocation by Graue <graue@oceanbase.org>; public domain */
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#include <stdlib.h>
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#include <limits.h>
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#include "err.h"
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/* MinGW (for example) appears to lack SIZE_T_MAX. */
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#ifndef SIZE_T_MAX
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#define SIZE_T_MAX ULONG_MAX
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#endif
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/*
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* The usual xmalloc and xrealloc type routines, for allocating memory
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* and bombing out if it fails.
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*
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* xm and xr here take two values: size and nmemb, like fread/fwrite.
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* The idea is to be able to check for overflow, to prevent some weird
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* crashes and security problems that can arise if you multiply size
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* and nmemb and they overflow.
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*/
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/* FIXME: use %zu (size_t) in these format arguments if library is C99 */
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/*
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* Multiply size and number of elements, bombing out if overflow would
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* occur.
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* Note: In the case where size*nmemb is exactly equal to SIZE_T_MAX,
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* this function considers that an overflow, even though it isn't
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* really. But it's not likely the program will get that much memory,
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* anyway.
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*/
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static size_t sizmul(size_t size, size_t nmemb)
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{
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if (SIZE_T_MAX / size <= nmemb)
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{
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errx(1, "allocating %lu objects of size %lu "
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"would overflow", (unsigned long)nmemb,
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(unsigned long)size);
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}
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return size * nmemb; /* won't overflow */
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}
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static void nomem(size_t size, size_t nmemb)
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{
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err(1, "cannot allocate %lu objects of size %lu "
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"(total %lu bytes)", (unsigned long)nmemb,
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(unsigned long)size, (unsigned long)(nmemb*size));
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}
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void *xm(size_t size, size_t nmemb)
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{
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const size_t bytes = sizmul(size, nmemb);
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void *p;
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p = malloc(bytes);
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if (p == NULL) nomem(size, nmemb);
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return p;
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}
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void *xr(void *p, size_t size, size_t nmemb)
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{
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const size_t bytes = sizmul(size, nmemb);
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p = realloc(p, bytes);
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if (p == NULL) nomem(size, nmemb);
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return p;
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}
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/* expand array */
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void *xpnd(void *p, int nit, int *sit, size_t sz)
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{
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if (nit < *sit) return p;
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else if (*sit > 0) return xr(p, sz, (*sit *= 2));
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else return xm(sz, (*sit = 10));
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}
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