On 03/24/2016 05:32 AM, Martin Richtarsky wrote:
Hi all,
we are using the -fstack-protector compiler option with gcc 5.x to detect
stack smashing. While analyzing a performance regression resulting from
this I found the instrumentation is also done for our STL string
implementation which has an interned buffer for short strings. So
basically a function having an object of that string class on the stack
would incur some performance overhead due to checking, although it can be
argued that the string class is pretty safe.
Is there a way of excluding either a class or a class member from
triggering the instrumentation?
I have noticed that switching to wchar_t (e.g. unsigned short on x86)
already removes the checking, which means that STL wstring is not checked.
However, there is no 1 byte type I could use for string which avoids the
checking.
Any ideas?
Florian's response made this thread bubble up in my Inbox. Although
I haven't tested it on an example like you describe, its possible
that #pragma GCC optimize ("-fno-stack-protector") or the equivalent
attribute might do what you're looking for (it can be used with
functions, not whole classes). One caveat to keep in mind is that
there have been problems with the #pragma (the FAQ on the Wiki has
some details:
https://gcc.gnu.org/wiki/FAQ#optimize_attribute_broken).
Martin
