On Wed, Oct 12, 2016 at 5:49 PM, Rob Landley <r...@landley.net> wrote: > > So... no? I think? Is there a way _I_ can tag this? (I can't do my own > vfork prototype because I can't #undef the one I get out of unistd.h and > that's a fairly generic header. It's sad I can't redo function > prototypes after the fact, but the language never gave me a way to. > Maybe I could do a gratuitous wrapper around it?) >
gcc seems to do the equivalent automatically for any function named "vfork": https://github.com/gcc-mirror/gcc/blob/e11be3ea01eaf8acd8cd86d3f9c427621b64e6b4/gcc/calls.c#L533 On Thu, Oct 13, 2016 at 1:03 AM, Rob Landley <r...@landley.net> wrote: > > If I have to gratuitously call setjmp() and ignore its return value > right before calling vfork() to beat reliable behavior out of gcc, I can > do that. I can also use global variables instead of local variables, or > make a structure of local variables so gcc can't gratuitously reorganize > them and trim the stack, or have my one allowed <strike>phone</strike> > function call be to a function I define that contains "everything the > child does" to preserve the stack context. > > Personally, I'd rather the compiler didn't fight me when I'm trying to > do something obvious, but I have LOTS of ways to fight back. :) It doesn't seem like gcc differentiates between vfork, setjmp, etc. so it's presumably providing some behavior that satisfies the constraints of all of them (or there's a bug). The specification for longjmp says that only non-volatile local variables that get modified have unspecified values, so you could maybe try sprinkling volatile on things to see if it makes your problem go away?
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