I was tired of writing this over and over:

double* data = (double*)malloc(20 * sizeof(double));
if (data == NULL) {
  fputs("out of memory", stderr);
  abort();
}

And today I learned that there's a family of e___() functions like emalloc() and ecalloc() which will exit the process if the malloc()-returned pointer is NULL. These functions are only present in the BSD family of operating system's util.h system header. They aren't standard C functions.

#include <util.h>

void (*)(int, const char *, ...) esetfunc(void (*)(int, const char *, ...));

int easprintf(char ** restrict str, const char * restrict fmt, ...);

FILE * efopen(const char *p, const char *m);

void * ecalloc(size_t n, size_t s);

void * emalloc(size_t n);

void * erealloc(void *p, size_t n);

void ereallocarr(void *p, size_t n, size_t s);

char * estrdup(const char *s);

char * estrndup(const char *s, size_t len);

size_t estrlcat(char *dst, const char *src, size_t len);

size_t estrlcpy(char *dst, const char *src, size_t len);

intmax_t estrtoi(const char * nptr, int base, intmax_t lo, intmax_t hi);

uintmax_t estrtou(const char * nptr, int base, uintmax_t lo, uintmax_t hi);

int evasprintf(char ** restrict str, const char * restrict fmt, ...);

The easprintf(), efopen(), ecalloc(), emalloc(), erealloc(), ereallocarr(), estrdup(), estrndup(), estrlcat(), estrlcpy(), estrtoi(), estrtou(), and evasprintf() functions operate exactly as the corresponding functions that do not start with an e except that in case of an error, they call the installed error handler that can be configured with esetfunc().

For the string handling functions, it is an error when the destination buffer is not large enough to hold the complete string. For functions that allocate memory or open a file, it is an error when they would return a null pointer. The default error handler is err(). The function esetfunc() returns the previous error handler function. A NULL error handler will just call exit().

— emalloc(3) - NetBSD Manual Pages

These functions are relatively simple. You can easily implement them yourself.

// I don't know if static or inline is better.
inline void * emalloc(size_t n) {
  void *p = malloc(n);
  if (p == NULL) {
    fputs("out of memory", stderr);
    abort();
  }
  return p;
}

// Do the same wrapper thing for all the other functions.

I just thought it was cool that this was a thing that is built into an operating system's C standard library. That's batteries included for sure.

What do other languages do on out-of-memory errors?

• Java: Throw an exception
• C++: Throw an exception
• Rust: Abort or panic
• JavaScript: Crash the engine
• Python: Throws a special exception
• Go: Terminate

And then there's C: Return a null pointer. 🤷‍♀️ Great if you need that control, a hassle if you want the happy path.