On this GCC Internals page http://en.wikibooks.org/wiki/GNU_C_Compiler_Internals/GNU_C_Compiler_Architecture_3_4 I found the following in the "GCC Initialization" section: "GCC built-in functions are the functions that are evaluated at compile time. For example, if the size argument of a strcpy() function is a constant then GCC replaces the function call with the required number of assignments." I was curious about this, so I tried compiling to assembly (-S) a very simple program: #include <stdio.h> #include <stdlib.h> #include <string.h> int main(void) { char s1[0x10]; char * s0 = "HELLO"; strcpy(s1, s0); printf("%s %s\n", s0, s1); return EXIT_SUCCESS; } But the resulting assembly code simply calls strcpy with the two arguments, just as I would have expected had I not read the above sentence: movq $.LC0, -40(%rbp) movq -40(%rbp), %rdx leaq -32(%rbp), %rax movq %rdx, %rsi movq %rax, %rdi call strcpy (Here, .LC0 labels the string "HELLO".) So what does that sentence actually mean and what am I missing? Thanks! Amittai Aviram PhD Student in Computer Science Yale University 646 483 2639 amittai.aviram@xxxxxxxx http://www.amittai.com
