-qstackprotect

Pragma equivalent

None.

Purpose

Provides protection against malicious code or programming errors that overwrite or corrupt the stack.

Syntax


        .-nostackprotect-.                          
>>- -q--+-stackprotect---+----=----+-all--------+--------------><
                                   '-size--=--N-'

Defaults

-qnostackprotect

Parameters

all: all protects all procedures whether or not there are vulnerable objects. This option is not set by default.
size=N: size=N protects all procedures containing automatic objects greater or equal to N bytes in size. The default size is 8 when -qstackprotect is enabled.
Note: When both all and size are used, the last option wins.

Usage

-qstackprotect generates extra code to protect procedures with vulnerable objects against stack corruption. This option is disabled by default because it can cause performance degradation. The default option is -qnostackprotect.

To generate code to protect all procedures with vulnerable objects:

xlc myprogram.c -qstackprotect=all

To generate code to protect procedures with objects of certain bytes:

xlc myprogram.c -qstackprotect=size=8

Note:

This option cannot be used with #pragma options.
Because of the dependency on libc.a in AIX®, this option requires the following AIX levels:
- AIX 5.3/TL11 and up.
- AIX 6.1/TL4 and up.
If the link step fails with a message that indicates __ssp_canary_word is undefined, you have probably used an unsupported level of AIX.

Predefined macros