Hi, On Fri, 28 Feb 2020, Jon Turney wrote:
> Mentioning the stack pointer in the clobber list is now a gcc warning. > > We never wanted gcc to try to restore %esp after this (x86-specific) > asm, since the whole point of the inline asm here is to adjust %esp to > satisfy alignment, so remove %esp from the asm clobber list. > > Of more concern is the alleged requirement that %esp must be unchanged > over an asm statement (which makes what this code is trying to do > impossible to write as a C function), although on x86 we are probably ok > in this particular instance. > > ../../../../winsup/cygwin/init.cc: In function 'void threadfunc_fe(void*)': > ../../../../winsup/cygwin/init.cc:33:46: error: listing the stack pointer > register '%esp' in a clobber list is deprecated [-Werror=deprecated] > ../../../../winsup/cygwin/init.cc:33:46: note: the value of the stack pointer > after an 'asm' statement must be the same as it was before the statement > > Also, because we now using gcc's "basic" rather than "extended" asm > syntax we don't need to escape the '%' in '%esp' as '%%esp'. > --- > > Notes: > N.B: This comes with a 'this should be ok, but I haven't actually > tested that x86 Cygwin works after this' caveat. We run with this patch in Git for Windows for quite a while, and I have yet to hear complaints: https://github.com/git-for-windows/msys2-runtime/commit/dd5aa267f6f28aef2a241cc7a01bb71a434b403c As far as I can tell, MSYS2 does the same. So there is at least some confirmation to be had ;-) Ciao, Dscho > > winsup/cygwin/crt0.c | 2 +- > winsup/cygwin/init.cc | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/winsup/cygwin/crt0.c b/winsup/cygwin/crt0.c > index fee4b2e24..9fcebd8fa 100644 > --- a/winsup/cygwin/crt0.c > +++ b/winsup/cygwin/crt0.c > @@ -27,7 +27,7 @@ mainCRTStartup () > #if __GNUC_PREREQ(6,0) > #pragma GCC diagnostic pop > #endif > - asm volatile ("andl $-16,%%esp" ::: "%esp"); > + asm volatile ("andl $-16,%esp"); > #endif > > cygwin_crt0 (main); > diff --git a/winsup/cygwin/init.cc b/winsup/cygwin/init.cc > index 851a7ffed..7ae7d08fe 100644 > --- a/winsup/cygwin/init.cc > +++ b/winsup/cygwin/init.cc > @@ -30,7 +30,7 @@ threadfunc_fe (VOID *arg) > #if __GNUC_PREREQ(6,0) > #pragma GCC diagnostic pop > #endif > - asm volatile ("andl $-16,%%esp" ::: "%esp"); > + asm volatile ("andl $-16,%esp"); > #endif > _cygtls::call ((DWORD (*) (void *, void *)) TlsGetValue (_my_oldfunc), > arg); > } > -- > 2.21.0 > >
