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    <p>I don't know the cross-platform answer to your question. But this made me curious. So what do we do? Look at the stack!</p> <p>For the first iteration:</p> <p>test.c</p> <pre><code>int main(void) { return 0; } </code></pre> <p>test2.c</p> <pre><code>int main(int argc, char *argv[]) { return 0; } </code></pre> <p>And now look at the assembly output:</p> <pre><code>$ gcc -S -o test.s test.c $ cat test.s .file "test.c" .text .globl main .type main, @function main: pushl %ebp movl %esp, %ebp movl $0, %eax popl %ebp ret .size main, .-main .ident "GCC: (Ubuntu 4.4.3-4ubuntu5) 4.4.3" .section .note.GNU-stack,"",@progbits </code></pre> <p>Nothing exciting here. Except for one thing: <strong>both C programs have the same assembly output!</strong></p> <p>This basically makes sense; we never really have to push/pop anything off of the stack for main(), since it's the first thing on the call stack.</p> <p>So then I wrote this program:</p> <pre><code>int main(int argc, char *argv[]) { return argc; } </code></pre> <p>And its asm:</p> <pre><code>main: pushl %ebp movl %esp, %ebp movl 8(%ebp), %eax popl %ebp ret </code></pre> <p>This tells us that "argc" is located at <code>8(%ebp)</code> </p> <p>So now for two more C programs:</p> <pre><code>int main(int argc, char *argv[]) { __asm__("movl 8(%ebp), %eax\n\t" "popl %ebp\n\t" "ret"); /*return argc;*/ } int main(void) { __asm__("movl 8(%ebp), %eax\n\t" "popl %ebp\n\t" "ret"); /*return argc;*/ } </code></pre> <p>We've stolen the "return argc" code from above and pasted it into the asm of these two programs. When we compile and run these, and then invoke <code>echo $?</code> (which echos the return value of the previous process) we get the "right" answer. So when I run "./test a b c d" then <code>$?</code> gives me "5" for both programs - even though only one has argc/argv defined. This tells me that, on my platform, argc is for sure placed on the stack. I'd bet that a similar test would confirm this for argv.</p> <p>Try this on Windows!</p>
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    1. POWhen main is defined without parameters, will argc and argv still be present on the stack?
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    1. POWhen main is defined without parameters, will argc and argv still be present on the stack?
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    1. COif they are present or not it depends on the startup code, not by how main is defined. Theoretically compilers can choose which startup code to give according to the definition, in this case I would create a new expression, "reversed overloading" on the main func (the caller is changed according to how callee is "defined"). It does not happen on every test I was able to do: startup code is always the same regardless of how main is defined. And this is why I prefer the usage of `int main()` for systems where the startup code pass two args (argc and argv), instead of `int main(void)`.
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