g77 -fPIC failures. was: Results for egcs-2.93.20 19990429 (gcc2 ss-980929 experimental) testsuite on i686-pc-sco3.2v5.0.5

[Robert Lipe <robertlipe@usa.net>]

Since this was a regression, I started to dig into this a little deeper.

> Could someone with an SCO system look into these failures?  They don't
> occur on other i686 targets, AFAICT, or on i686-pc-sco for -mcoff
> instead of -fPIC (if I'm reading these test results right).

-mcoff and -fPIC are rather different and even incompaptible.
Interestingly, these failures don't show up on even the SVR5/x86 targets
even in PIC mode.

I walked back through my logs.  These passed on 4/13 but failed on 4/24.
(I don't recall why OpenServer wouldn't build for that week and a half
but at least that gives us a range of ChangeLogs to parse.)   This was
right at the peak of the i386 overhaul.

I looked at 970816-3.f.  If I add -static to the link line, I get
believable output.  Only if it's dyanmic and PIC does it fail
to execute.  Unfortunately, it looks like it's dropping core in
/usr/lib/libc.so.1 if the GDB output can be believed:

Program received signal SIGSEGV, Segmentation fault.
0x80016ce6 in ?? () from /usr/lib/libc.so.1
(gdb) where
#0  0x80016ce6 in ?? () from /usr/lib/libc.so.1
#1  0x80016bcc in ?? () from /usr/lib/libc.so.1
#2  0x800181dd in ?? () from /usr/lib/libc.so.1
#3  0x8001929d in ?? () from /usr/lib/libc.so.1
#4  0x80014a90 in ?? () from /usr/lib/libc.so.1

PIC and dynamic linking on x86 is pretty mysterious to me.  How should
we debug this?  I can walk the tree (or at least specific files) back in
time to spot the exact date it broke but that's a pretty icky way to do
it.

> >Running target unix/-fPIC
> >FAIL: g77.f-torture/execute/970816-3.f execution,  -O0 
> >FAIL: g77.f-torture/execute/970816-3.f execution,  -O1 
> >FAIL: g77.f-torture/execute/970816-3.f execution,  -O2 
> >FAIL: g77.f-torture/execute/970816-3.f execution,  -O2 -fomit-frame-pointer -finline-functions 
> >FAIL: g77.f-torture/execute/970816-3.f execution,  -Os 
> >FAIL: g77.f-torture/execute/971102-1.f execution,  -O0 
> >FAIL: g77.f-torture/execute/971102-1.f execution,  -O1 
> >FAIL: g77.f-torture/execute/971102-1.f execution,  -O2 
> >FAIL: g77.f-torture/execute/971102-1.f execution,  -O2 -fomit-frame-pointer -finline-functions 
> >FAIL: g77.f-torture/execute/971102-1.f execution,  -O2 -fomit-frame-pointer -finline-functions -funroll-loops 
> >FAIL: g77.f-torture/execute/971102-1.f execution,  -O2 -fomit-frame-pointer -finline-functions -funroll-all-loops 
> >FAIL: g77.f-torture/execute/971102-1.f execution,  -Os 
> >FAIL: g77.f-torture/execute/u77-test.f execution,  -O0 
> >FAIL: g77.f-torture/execute/u77-test.f execution,  -O1 
> >FAIL: g77.f-torture/execute/u77-test.f execution,  -O2 
> >FAIL: g77.f-torture/execute/u77-test.f execution,  -O2 -fomit-frame-pointer -finline-functions 
> >FAIL: g77.f-torture/execute/u77-test.f execution,  -O2 -fomit-frame-pointer -finline-functions -funroll-loops 
> >FAIL: g77.f-torture/execute/u77-test.f execution,  -O2 -fomit-frame-pointer -finline-functions -funroll-all-loops 
> >FAIL: g77.f-torture/execute/u77-test.f execution,  -Os