Linux的path_alloc函數

#include "apue.h" #include <errno.h> #include <limits.h> #ifdef   PATH_MAX static int   pathmax = PATH_MAX; #else static int   pathmax = 0; #endif #define SUSV3 200112L static long posix_version = 0; /* If PATH_MAX is indeterminate, no guarantee this is adequate */#define PATH_MAX_GUESS   1024 char * path_alloc(int *sizep) /* also return allocated size, if nonnull */{ char *ptr; int size; if (posix_version == 0)        posix_version = sysconf(_SC_VERSION); if (pathmax == 0) {     /* first time through */       errno = 0;       /* From: http://www.bianceng.cn */       if ((pathmax = pathconf("/", _PC_PATH_MAX)) < 0) {          if (errno == 0)             pathmax = PATH_MAX_GUESS; /* it's indeterminate */         else            err_sys("pathconf error for _PC_PATH_MAX");        } else {          pathmax++;    /* add one since it's relative to root */       } } if (posix_version < SUSV3)        size = pathmax + 1; else       size = pathmax; if ((ptr = malloc(size)) == NULL)        err_sys("malloc error for pathname"); if (sizep != NULL)        *sizep = size; return(ptr); }     或char*path_alloc(int* size){char *p = NULL;if(!size) return NULL;p = malloc(256);if(p)*size = 256;else*size = 0;return p;}