Below is the code that includes the variational function and calls the variational function. I would expect it to output each sequence of numbers appropriately. This happens when compiling as a 32-bit executable, but not when compiling as a 64-bit executable.
#include <stdarg.h>
#include <stdio.h>
#ifdef _WIN32
#define SIZE_T_FMT "%Iu"
#else
#define SIZE_T_FMT "%zu"
#endif
static void dumpargs(size_t count, ...) {
size_t i;
va_list args;
printf("dumpargs: argument count: " SIZE_T_FMT "\n", count);
va_start(args, count);
for (i = 0; i < count; i++) {
size_t val = va_arg(args, size_t);
printf("Value=" SIZE_T_FMT "\n", val);
}
va_end(args);
}
int main(int argc, char** argv) {
(void)argc;
(void)argv;
dumpargs(1, 10);
dumpargs(2, 10, 20);
dumpargs(3, 10, 20, 30);
dumpargs(4, 10, 20, 30, 40);
dumpargs(5, 10, 20, 30, 40, 50);
return 0;
}
Here is the result when compiled for 64 bit:
dumpargs: argument count: 1
Value=10
dumpargs: argument count: 2
Value=10
Value=20
dumpargs: argument count: 3
Value=10
Value=20
Value=30
dumpargs: argument count: 4
Value=10
Value=20
Value=30
Value=14757395255531667496
dumpargs: argument count: 5
Value=10
Value=20
Value=30
Value=14757395255531667496
Value=14757395255531667506
Edit:
Note that the reason a variable function pulls out size_tis because in the real world it is used for a variational function that takes a list of pointers and lengths. Naturally, the argument of length should be size_t. And in some cases, the caller may convey something known:
void myfunc(size_t pairs, ...) {
va_list args;
va_start(args, count);
for (i = 0; i < pairs; i++) {
const void* ptr = va_arg(args, const void*);
size_t len = va_arg(args, size_t);
process(ptr, len);
}
va_end(args);
}
void user(void) {
myfunc(2, ptr1, ptr1_len, ptr2, 4);
}
, 4, myfunc, , . , , sizeof strlen 4 size_t -. , ( ).
- , . , , .