[PATCH]: New warning option -Walloca

["Raksit Ashok" <raksit dot ashok at gmail dot com>]

Hi,

This patch adds a "-Walloca" option to gcc. If this warning is enabled, gcc
will emit a warning on encountering "alloca" calls. This option could be used
to enforce coding conventions that forbid use of alloca. For example:
http://www.dc.turkuamk.fi/docs/gnu/awk/gawk_21.html
http://www-unix.mcs.anl.gov/mpi/mpich/adi3/mpich2/node316.htm

Possible motivations for such a coding convention include:
(1) Portability issues with alloca.
(2) Enabling a stricter control over stack requirements;
    (no VLAs + no alloca's) => (bounded frame size), which is useful in the
    context of running thousands of threads with small stacks on 32-bit
    machines. Also small stacks in other contexts, such as embedded
    systems.

I have tested the patch on i686-linux. OK for mainline?

Thanks,
Raksit

------

gcc/ChangeLog

2007-08-30  Raksit Ashok <raksit.ashok@gmail.com>

	* doc/invoke.texi (Option Summary): Mention -Walloca.
	(Warning Options): Document -Walloca.
	* c.opt (Walloca): New flag.
	* c-parser.c (c_parser_postfix_expression_after_primary): New warning
	based on flag warn_alloca.


gcc/cp/ChangeLog

2007-08-30  Raksit Ashok <raksit.ashok@gmail.com>

	* parser.c (cp_parser_postfix_expression): New warning based on flag
	warn_alloca.


gcc/testsuite/ChangeLog

2007-08-30  Raksit Ashok <raksit.ashok@gmail.com>

	* gcc.dg/walloca.c: New test.
	* g++.dg/warn/Walloca.C: New test.

Attachment: walloca.txt
Description: Text document