An x86 -fpic and -fomit-frame-pointer bug

[Manfred Hollstein]

On Sat, 20 June 1998, 14:52:59, hjl@lucon.org wrote:

 > > 
 > > On Mon, 15 June 1998, 23:14:14, hjl@lucon.org wrote:
 > > 
 > >  > Hi,
 > >  > 
 > >  > Here is a test case for an x86 -fpic and -fomit-frame-pointer bug.
 > >  > cexp.cc is miscompiled by -fpic and -fomit-frame-pointer. Basically
 > >  > ebx saved on the stack is overriden by
 > >  > 
 > >  > 	fstpl (%esp)
 > >  > 
 > >  > Later,
 > >  > 
 > >  > 	popl %ebx
 > >  > 
 > >  > put some garbage in ebx. Without -fpic or -fomit-frame-pointer, cexp.s
 > >  > is compiled fine.
 > >  > 
 > >  > BTW, egcs 1.0.3 is ok. The last working egcs 1.1 is 971215 and 971225
 > >  > has the same bug.
 > > 
 > > H.J., your example is incomplete; the file "cexp.h" is missing!
 > > 
 > 
 > It shows you are the only one who ever tried my testcase :-). Here
 > is the complete testcase.

Thanks. BUT, egcs-1.0.3a is buggy, too:

$ LD_RUN_PATH=/tools/gnu/lib/gcc-lib/i586-linux/egcs-2.91.41 gmake CC=/tools/gnu/packages/egcs/19980620/bin/gcc 
/tools/gnu/packages/egcs/19980620/bin/gcc -S -O2 -fno-exceptions main.cc
/tools/gnu/packages/egcs/19980620/bin/gcc -S -fomit-frame-pointer -O3 -fpic -fno-exceptions  cexp.cc
/tools/gnu/packages/egcs/19980620/bin/gcc -o main main.s cexp.s -lstdc++
for f in main; do echo "Running: $f"; $f; \
  if [ $? != 0 ]; then echo Failed; fi; done
Running: main
Failed
$ LD_RUN_PATH=/tools/gnu/lib/gcc-lib/i586-linux/egcs-2.90.29 gmake CC=/tools/gnu/packages/egcs/1.0.3a/bin/gcc 
/tools/gnu/packages/egcs/1.0.3a/bin/gcc -S -O2 -fno-exceptions main.cc
/tools/gnu/packages/egcs/1.0.3a/bin/gcc -S -fomit-frame-pointer -O3 -fpic -fno-exceptions  cexp.cc
/tools/gnu/packages/egcs/1.0.3a/bin/gcc -o main main.s cexp.s -lstdc++
for f in main; do echo "Running: $f"; $f; \
  if [ $? != 0 ]; then echo Failed; fi; done
Running: main
Failed
$ make clean

Interestingly, gcc-2.8.1 is OK:

$ LD_RUN_PATH=/tools/gnu/lib/gcc-lib/i586-linux/2.8.1 gmake CC=/tools/gnu/packages/gcs/2.8.1/bin/gcc 
/tools/gnu/packages/gcs/2.8.1/bin/gcc -S -O2 -fno-exceptions main.cc
/tools/gnu/packages/gcs/2.8.1/bin/gcc -S -fomit-frame-pointer -O3 -fpic -fno-exceptions  cexp.cc
/tools/gnu/packages/gcs/2.8.1/bin/gcc -o main main.s cexp.s -lstdc++
for f in main; do echo "Running: $f"; $f; \
  if [ $? != 0 ]; then echo Failed; fi; done
Running: main
22.1672, 1.04274

manfred