On 30 January 2011 20:45, Amittai Aviram wrote: > 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! strcpy has no 'size' parameter, I assume it's meant to say strncpy
