function pragma

Tells the compiler to generate calls to functions specified in the pragma's argument list, instead of inlining them.


#pragma function( function1 [ , function2 ... ] )


Intrinsic functions are normally generated as inline code, not as function calls. If you use the intrinsic pragma or the /Oi compiler option to tell the compiler to generate intrinsic functions, you can use the function pragma to explicitly force a function call. Once a function pragma is seen, it takes effect at the first function definition that contains a specified intrinsic function. The effect continues to the end of the source file, or to the appearance of an intrinsic pragma specifying the same intrinsic function. You can only use the function pragma outside of a function, at the global level.

For lists of the functions that have intrinsic forms, see intrinsic pragma.


// pragma_directive_function.cpp
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// use intrinsic forms of memset and strlen
#pragma intrinsic(memset, strlen)

// Find first word break in string, and set remaining
// chars in string to specified char value.
char *set_str_after_word(char *string, char ch) {
   int i;
   int len = strlen(string);  /* NOTE: uses intrinsic for strlen */

   for(i = 0; i < len; i++) {
      if (isspace(*(string + i)))

   for(; i < len; i++)
      *(string + i) = ch;

   return string;

// do not use strlen intrinsic
#pragma function(strlen)

// Set all chars in string to specified char value.
char *set_str(char *string, char ch) {
   // Uses intrinsic for memset, but calls strlen library function
   return (char *) memset(string, ch, strlen(string));

int main() {
   char *str = (char *) malloc(20 * sizeof(char));

   strcpy_s(str, sizeof("Now is the time"), "Now is the time");
   printf("str is '%s'\n", set_str_after_word(str, '*'));
   printf("str is '%s'\n", set_str(str, '!'));
str is 'Now************'
str is '!!!!!!!!!!!!!!!'

See also

Pragma directives and the __pragma and _Pragma keywords