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XMALLOC(3pub) C Programmer's Manual XMALLOC(3pub)


xmalloc, xrealloc, xfree, xstrdup, xmemdup, memdup - memory allocation functions for Publib


#include <publib.h>

void *xmalloc(size_t bytes);
void *xrealloc(void *ptr, size_t bytes);
void xfree(void *ptr);
char *xstrdup(const char *string);
void *memdup(const void *mem, size_t bytes);
void *xmemdup(const void *mem, size_t bytes);


These functions are utility functions for memory allocation from the publib library. xmalloc, xrealloc, and xfree are error checking versions of the standard library routines malloc, realloc, and free, respectively. They are guaranteed to never return unless there was no problem: if, for example, xmalloc is unable to allocate the requested amount of memory, it prints an error message and terminates the program. Hence, the caller does not need to check for a NULL return value, and the code that calls these functions is simpler due to the lack of error checks.

Similarly, xstrdup is an error checking version of the common (though not standard) strdup routine, which creates a duplicate of a string by allocating memory for the copy with malloc. (For systems that lack strdup, publib provides one in its portability module; it is always declared in <publib.h>.)

memdup is similar to strdup, it creates a copy of an arbitrary memory area (the arguments are a pointer to the beginning of the area, and its size) by allocating memory for the copy with malloc. xmemdup is its error checking version.


xmalloc and xrealloc treat a request to allocate a block of 0 bytes as an error. xrealloc will allow its first argument to be NULL.


publib(3), malloc(3), strdup(3)


Lars Wirzenius (

C Programmer's Manual Publib