Re: Trying to track down problem with packed.com from testsuite

[Gaius Mulley]

john o goyo <jog37@riddermarkfarm.ca> writes:

> Greetings, Gaius.
>
> On 2024-08-11 14:30, Gaius Mulley wrote:
>> john o goyo <jog37@riddermarkfarm.ca> writes:
>>
>>> Greetings, Gaius.
>>>
>>> Here is an oddity:
>>>
>>> [~/opt/gm2/testsuite]=> gm2-14 -c -O -fomit-frame-pointer
>>> -finline-functions -fiso packed.mod
>>> [~/opt/gm2/testsuite]=> gm2-14 -c -O0 -fomit-frame-pointer
>>> -finline-functions -fiso packed.mod
>>> [~/opt/gm2/testsuite]=> gm2-14 -c -O1 -fomit-frame-pointer
>>> -finline-functions -fiso packed.mod
>>> [~/opt/gm2/testsuite]=> gm2-14 -c -O2 -fomit-frame-pointer
>>> -finline-functions -fiso packed.mod
>>> gm2: internal compiler error: Segmentation Fault signal terminated
>>> program cc1gm2
>>> Please submit a full bug report, with preprocessed source (by using
>>> -freport-bug).
>>> See <https://gcc.gnu.org/bugs/> for instructions.
>>> [~/opt/gm2/testsuite]=> gm2-14 -c -Ofast -fomit-frame-pointer
>>> -finline-functions -fiso packed.mod
>>> gm2: internal compiler error: Segmentation Fault signal terminated
>>> program cc1gm2
>>> Please submit a full bug report, with preprocessed source (by using
>>> -freport-bug).
>>> See <https://gcc.gnu.org/bugs/> for instructions.
>>>
>>> Basically, optimisation level 2 and above causes problems.
>>>
>>> I am trying to chase down the problem but I have clue where the gm2
>>> compilation starts. Please inform me on which function to break.
>>>
>>> Sincerely,
>>> john
>> Hi John,
>>
>> that is an interesting observation.
>>
>> One way to debug is to set a break point on: 
>> gimplify_function_tree(tree_node*)
>>
>> which is called by the front end at each end of function when the
>> statement tree is complete.  The statement tree can be dumped as follows
>> below.  For small test programs this can be useful - even to see which
>> function causes the sigsegv.
>
> Perhaps I am missing something but how do I set a breakpoint on
> something in cc1gm2?  Does it not read files produced by gcc?
>
> I tried loading the core file but no backtrace available, as seen below.
>
> % gdb
>   /home/build/gcc/14.2.0/libexec/gcc/sparc-sun-solaris2.11/14.2.0/cc1gm2
>  core
> GNU gdb (GDB) 15.1
> [...]
> Reading symbols from
> /home/build/gcc/14.2.0/libexec/gcc/sparc-sun-solaris2.11/14.2.0/cc1gm2...
> [New LWP 1]
> Cannot access memory at address 0x1c
> Cannot access memory at address 0x18
> Cannot access memory at address 0x18
> Core was generated by
> `/home/build/gcc/14.1.0/libexec/gcc/sparc-sun-solaris2.11/14.1.0/cc1gm2
> -quiet -'.
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0  0xffbff4fc in ?? ()
> (gdb) bt
> #0  0xffbff4fc in ?? ()
> #1  0x00665e1c in alloc_page (order=0) at
>  /home/build/opt/gcc/src/gcc-14.2.0/gcc/ggc-page.cc:805
> #2  ggc_internal_alloc (size=<optimized out>, f=0xffbfe888,
>  s=4290766288, n=4170231808)
>     at /home/build/opt/gcc/src/gcc-14.2.0/gcc/ggc-page.cc:1295
> Backtrace stopped: previous frame identical to this frame (corrupt stack?)
>
> Sincerely,
> john

Hi John,

Does the following work on Solaris with gdb, it will invoke cc1gm2
with all default options and the source file hello.mod.


$ gm2 hello.mod -wrapper gdb,--args

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For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from 
/home/gaius/opt/libexec/gcc/x86_64-pc-linux-gnu/15.0.0/cc1gm2...
(gdb) break gimplify_function_tree(tree_node*)
Breakpoint 1 at 0xe52080: file ../../gcc/tree.h, line 3632.
(gdb) run
Starting program: /home/gaius/opt/libexec/gcc/x86_64-pc-linux-gnu/15.0.0/cc1gm2 
-imultiarch x86_64-linux-gnu -quiet -dumpdir a- -dumpbase hello.mod 
-dumpbase-ext .mod -mtune=generic -march=x86-64 -g -fm2-pathname=- 
-fm2-pathnameI. -fgen-module-list=- -fscaffold-dynamic -fscaffold-main 
-flibs=m2cor,m2log,m2pim,m2iso -fm2-pathname=- -fm2-pathnameI. hello.mod -o 
/tmp/ccQdbK7K.s
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, gimplify_function_tree (fndecl=0x7ffff76cc300) at 
../../gcc/tree.h:3632
3632      if (TREE_CODE (__t) != __c)
(gdb)

If this feature doesn't work then you could add the two lines:

break gimplify_function_tree(tree_node*)
run -imultiarch x86_64-linux-gnu -quiet -dumpdir a- -dumpbase hello.mod \
-dumpbase-ext .mod -mtune=generic -march=x86-64 -g -fm2-pathname=- \
-fm2-pathnameI. -fgen-module-list=- -fscaffold-dynamic -fscaffold-main \
-flibs=m2cor,m2log,m2pim,m2iso -fm2-pathname=- -fm2-pathnameI. hello.mod \
-o hello.s

[ ie the command args specified in your Starting program line above, or
if -wrapper doesn't work, use gm2 -v hello.mod ].

to the end of gcc-source/gcc/gdbinit.in and then change directory to the
top build dir.

$ cd gcc
$ gdb cc1gm2

which will have the same effect, hope this helps

regards,
Gaius