calling main in ANSI C
Jim Patterson
jimp at cognos.UUCP
Tue Dec 4 01:59:43 AEST 1990
In article <814 at atcmpe.atcmp.nl> leo at atcmp.nl (!Leo Willems) writes:
>The ARM (the annotated C++ reference manual), section 3.4 states:
>
> "The function main() may not be called from within a program."
>
>I was looking for the same restriction in ANSI C, but could not find
>any statement in the ANSI C standard (2.1.2.2.1).
>Par. 2.1.2.2.3 (Program termination) states:
>
> "A return from the initial call to the main function...."
>
>The word "initial" suggests (to me) that main() may be called from within the
>program.
At least some implementations treat the function 'main' in a special
manner. Here's a snippet from a listing from VAX/VMS C V3.1-051 with
the "/machine_code" flag on:
146 int main(void) {
0000 main:
0000 0000 .entry main,^m<>
5E 08 C2 0002 subl2 #8,sp
00000000* EF 16 0005 jsb C$MAIN_ARGS
The subroutine C$MAIN_ARGS is only called by main, and the call is
generated automatically by the compiler. I believe that it's purpose is
to arrange for the argc and argv parameters to be provided to the main
entry point. It's my guess that if you tried to call main() with different
arguments with this compiler it wouldn't work (main would get the command
line arguments no matter what you did, or something worse would happen).
I won't hazard a guess as to whether this is considered legitimate
behaviour according to the standard.
--
Jim Patterson Cognos Incorporated
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