On Tue, Jul 23, 2013 at 3:02 PM, Florian Weimer <fwei...@redhat.com> wrote: > On 07/23/2013 09:51 PM, Andrew Pinski wrote: >> >> On Tue, Jul 23, 2013 at 12:48 PM, Florian Weimer <fwei...@redhat.com> >> wrote: >>> >>> We sometimes deal with code bases which use static local variables to cut >>> down frame size, for compatibility with legacy targets. Obviously, this >>> is >>> bad for thread safety. This new warning can be used to track down such >>> cases once you suspect they exist. >> >> >> Hmm, since you mentioned bad for thread safety but then I see in your >> patch you don't check to see if the variable is a thread local >> variable. Maybe you should not mention thread safety at all here or >> change the code not to include TLS variables. > > > Good point. What about this instead? > > Warn for variables declared inside functions which are static, but not > declared const. Such local variables can make functions not reentrant.
Do you envision this to be useful for C++ too? There are many bits here. 'const' in C++ does not necessary prevent race conditions with the variable's type has to run non-atomic constructors, or if the object has data members declared mutable, etc. It used to be idiomatic in C++ to use local statics in order to enforce initialization of "morally global" objects -- the function returns a pointer or reference to the object. I think the C++ ABI mandates that the implementation adds implicit locks to enforce orderly initialization -- Gaby
