Get command line arguments without arguments in main()

Question

One strange thing took my sleep away. .

I have P7 library. It is library for writing logs.

Library contains few examples. Example for C++ looks like:

int main(int i_iArgC, char* i_pArgV[])
{
   // Some code that don't use i_iArgC or i_pArgV
}

But the trick that program handle command line arguments somehow.
I play a little bit to make sure that this main called.
What I do:

Build in debug and set breakpoint on main (to make sure that exactly this main is called)
Changemain(int i_iArgC, char* i_pArgV[]) to main() (To make sure that no one use them)

I have no idea how it possible.

Here is minimal steps you can do to look on it by yourself:

Download P7 code from this page (link at top left)
Unzip archive
Run build.sh (It runs few makefiles in some order)
Execute Cpp_Example from Binaries folder
Execute again Cpp_Example /P7.Help to see that app react to command line arguments.

No define (MACRO) or flag to select other program entry point (which then redirect to `main`)? — Jarod42, Jul 25 '19 at 21:26
No. I don't found such tricks. Build is simple as possible and no way to hide such thing. But in one of Header files I found `#define P7TRACE_NO_VA_ARG_OPTIMIZATION` and `#include `. Maybe they use `stdarg.h` in some way to get arguments directly. — Stepan Loginov, Jul 25 '19 at 21:31

isanae · Accepted Answer · 2019-07-26T04:01:05.763

1

Most systems allow for getting the command line parameters without relying on main(). On Windows for example, you can use GetCommandLineW().

The library has non-portable code to do just that in Shared/Platforms/*/PProcess.h. A quick look at Windows_x86/PProcess.h shows that it uses GetCommandLineW() and the same file in Linux_x86/ reads /proc/self/cmdline.

edited Jul 26 '19 at 04:01

answered Jul 25 '19 at 22:21

isanae

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Get command line arguments without arguments in main()

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