[Bug pch/45979] New: precompiled headers breakage on 2.6.36-rc Linux/ARM kernels

["mikpe at it dot uu.se" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45979

           Summary: precompiled headers breakage on 2.6.36-rc Linux/ARM
                    kernels
           Product: gcc
           Version: 4.4.5
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: pch
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mikpe@it.uu.se


Recently I've started seeing massive pch test suite failures with gcc,
both trunk and 4.4, on armv5tel-linux-gnueabi:

FAIL: gcc.dg/pch/common-1.c  -O2  -I. (test for excess errors)
FAIL: gcc.dg/pch/common-1.c  -O2  assembly comparison
FAIL: gcc.dg/pch/common-1.c  -O3 -fomit-frame-pointer  -I. (test for excess
errors)
FAIL: gcc.dg/pch/common-1.c  -O3 -fomit-frame-pointer  assembly comparison
FAIL: gcc.dg/pch/counter-1.c -O0 -g -I. (test for excess errors)
FAIL: gcc.dg/pch/counter-1.c -O0 -g assembly comparison
FAIL: gcc.dg/pch/counter-1.c  -O3 -g  -I. (test for excess errors)
FAIL: gcc.dg/pch/counter-1.c  -O3 -g  assembly comparison
FAIL: gcc.dg/pch/cpp-1.c -O0 -g -I. (test for excess errors)
FAIL: gcc.dg/pch/cpp-1.c -O0 -g assembly comparison
...(many many more)

These failures started after I did a major update of the Linux distro
I run on my ARM boxes.  I reverted a few likely suspects (glibc and
the system gcc) to their earlier known-good versions, without effect,
but in the end the failures were traced to the Linux kernel:

- running linux-2.6.36-rc6 causes these PCH failures
- reverting to linux-2.6.35 (similar .config) makes PCH tests pass again
- pre-2.6.35 kernels are also known good

The PCH test suite failures come from ICEs in cc1.  I saved a core dump
of which gdb says the following:

Core was generated by `/home/mikpe/objdir/gcc/cc1 -quiet -I. -I. -iprefix
/home/mikpe/temp/lib/gcc/arm'.
Program terminated with signal 11, Segmentation fault.
#0  linemap_lookup (set=0x40215000, line=73) at
/home/mikpe/gcc-4.4-20100921/libcpp/line-map.c:284
284       if (line >= cached->start_location)
Missing separate debuginfos, use: debuginfo-install glibc-2.10.2-1.bl8.armv5tel
gmp-4.3.2-1.bl11.armv5tel mpfr-2.4.2-2.bl11.armv5tel
(gdb) bt
#0  linemap_lookup (set=0x40215000, line=73) at
/home/mikpe/gcc-4.4-20100921/libcpp/line-map.c:284
#1  0x000cbed0 in diagnostic_report_current_module (context=0x790888)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:236
#2  0x000cbffc in diagnostic_report_current_function (context=0xa4680042,
diagnostic=0x49)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:218
#3  0x000cc240 in default_diagnostic_starter (context=0xa4680042,
diagnostic=0x49)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:263
#4  0x000cb6c4 in diagnostic_report_diagnostic (context=0x790888,
diagnostic=0xbe88b8e0)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:403
#5  0x000cb940 in internal_error (gmsgid=0x6ecd70 "%s")
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:658
#6  0x00261cec in crash_signal (signo=-1098336032) at
/home/mikpe/gcc-4.4-20100921/gcc/toplev.c:601
#7  <signal handler called>
#8  linemap_lookup (set=0x40215000, line=73) at
/home/mikpe/gcc-4.4-20100921/libcpp/line-map.c:284
#9  0x000cbed0 in diagnostic_report_current_module (context=0x790888)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:236
#10 0x000cbffc in diagnostic_report_current_function (context=0xa4680042,
diagnostic=0x49)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:218
#11 0x000cc240 in default_diagnostic_starter (context=0xa4680042,
diagnostic=0x49)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:263
#12 0x000cb6c4 in diagnostic_report_diagnostic (context=0x790888,
diagnostic=0xbe88bcf8)
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:403
#13 0x000cbab0 in fatal_error (gmsgid=0x5ca9f0 "had to relocate PCH")
    at /home/mikpe/gcc-4.4-20100921/gcc/diagnostic.c:640
#14 0x0015da80 in gt_pch_restore (f=0xbe88bcf8) at
/home/mikpe/gcc-4.4-20100921/gcc/ggc-common.c:576
#15 0x00054608 in c_common_read_pch (pfile=0x134f170, name=0x1347a68
"./valid-6.h.gch", 
    fd=<value optimized out>, orig_name=<value optimized out>)
    at /home/mikpe/gcc-4.4-20100921/gcc/c-pch.c:420
#16 0x00574a8c in should_stack_file (import=<value optimized out>, file=<value
optimized out>, 
    pfile=<value optimized out>) at
/home/mikpe/gcc-4.4-20100921/libcpp/files.c:710
#17 _cpp_stack_file (import=<value optimized out>, file=<value optimized out>, 
    pfile=<value optimized out>) at
/home/mikpe/gcc-4.4-20100921/libcpp/files.c:795
#18 0x0056c168 in do_include_common (pfile=0x134f170, type=IT_INCLUDE)
    at /home/mikpe/gcc-4.4-20100921/libcpp/directives.c:784
#19 0x0056d028 in _cpp_handle_directive (pfile=0x134f170, indented=<value
optimized out>)
    at /home/mikpe/gcc-4.4-20100921/libcpp/directives.c:488
#20 0x00579d60 in _cpp_lex_token (pfile=0x134f170) at
/home/mikpe/gcc-4.4-20100921/libcpp/lex.c:1265
#21 0x0057d3bc in cpp_get_token (pfile=0x134f170) at
/home/mikpe/gcc-4.4-20100921/libcpp/macro.c:1235
#22 0x0057d620 in cpp_get_token_with_location (pfile=0x5ca9f0, loc=0xa1000)
    at /home/mikpe/gcc-4.4-20100921/libcpp/macro.c:1347
#23 0x0000c750 in c_lex_with_flags (value=0xbe88bf20, loc=0xbe88bf24,
cpp_flags=0x0, lex_flags=0)
    at /home/mikpe/gcc-4.4-20100921/gcc/c-lex.c:306
#24 0x00055114 in c_lex_one_token (parser=0xbe88bf1c, token=0xbe88bf1c)
    at /home/mikpe/gcc-4.4-20100921/gcc/c-parser.c:201
#25 0x000628c0 in c_parser_peek_token (parser=<value optimized out>,
parser=<value optimized out>)
    at /home/mikpe/gcc-4.4-20100921/gcc/c-parser.c:310
#26 c_parse_file (parser=<value optimized out>, parser=<value optimized out>)
    at /home/mikpe/gcc-4.4-20100921/gcc/c-parser.c:8324
#27 0x00049e3c in c_common_parse_file (set_yydebug=<value optimized out>)
    at /home/mikpe/gcc-4.4-20100921/gcc/c-opts.c:1252
#28 0x00263e24 in compile_file () at
/home/mikpe/gcc-4.4-20100921/gcc/toplev.c:970
#29 do_compile () at /home/mikpe/gcc-4.4-20100921/gcc/toplev.c:2197
---Type <return> to continue, or q <return> to quit---
#30 toplev_main () at /home/mikpe/gcc-4.4-20100921/gcc/toplev.c:2229
#31 0x4018c3e0 in __libc_start_main () from /lib/libc.so.6
#32 0x0000aef0 in _start ()

Note #13.  Apparently gcc "had to relocate PCH" (whatever that means) and
tries to issue a diagnostic, which fails miserably in linemap_lookup.

I also noticed many kernel messages about alignment traps in cc1, with PC
values in linemap_lookup().

I'll try to bisect the 2.6.36-rc kernel changes to see what caused the PCH
breakage.  But even if this turns out to be a kernel bug (as opposed to the
kernel just doing something different but valid), I don't think it's Ok for gcc
to SEGV if it "had to relocate PCH".