On Tue, Oct 2, 2012 at 8:31 PM, Ian Lance Taylor <[email protected]> wrote:
>>>>> > On a related issue, it looks to me that the compiler itself should be
>>>>> > compiled with -funwind-tables, otherwise there are no backtraces
>>>>> > generated, even if libbacktrace is linked in and operational. Again,
>>>>> > x86_64-linux-gnu host defaults to this flag, but other hosts are left
>>>>> > behind.
>>>>>
>>>>> Compiling with C++ should always give us -funwind-tables.
>>>>
>>>> It doesn't give that, because the compiler is compiled with
>>>> -fno-exceptions -fno-rtti.
>>>
>>> I believe in the long term we would to drop either of those.
>>
>> For the short term, I am bootstrapping attached patch, that adds
>> -funwind-tables to other noexcept flags.
>
> I think you should use -fasynchronous-unwind-tables here. That way we
> can get a backtrace if the compiler gets a segmentation violation.
>
> I'll approve this patch with that change. But you might want to check
> whether you can see any change in bootstrap time or compiler size
> (sorry).
There is slight increase in bootstrap compile time with expected
differences in .debug_frame and .eh_frame sections, but decrease in
overal size of the executables. Bootstrap on alphaev68-pc-linux-gnu
native, c,c++ languages only:
real 139m1.755s
user 437m33.065s
sys 17m54.324s
88266972 Oct 3 01:07 cc1
106976374 Oct 3 01:07 cc1plus
readelf -S gcc/cc1
There are 42 section headers, starting at offset 0x5287728:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .interp PROGBITS 00000001200002a8 000002a8
0000000000000013 0000000000000000 A 0 0 1
[ 2] .note.ABI-tag NOTE 00000001200002bc 000002bc
0000000000000020 0000000000000000 A 0 0 4
[ 3] .hash HASH 00000001200002e0 000002e0
00000000000154d0 0000000000000008 A 5 0 8
[ 4] .gnu.hash GNU_HASH 00000001200157b0 000157b0
000000000000be78 0000000000000000 A 5 0 8
[ 5] .dynsym DYNSYM 0000000120021628 00021628
0000000000030e88 0000000000000018 A 6 1 8
[ 6] .dynstr STRTAB 00000001200524b0 000524b0
000000000004aec9 0000000000000000 A 0 0 1
[ 7] .gnu.version VERSYM 000000012009d37a 0009d37a
0000000000004136 0000000000000002 A 5 0 2
[ 8] .gnu.version_r VERNEED 00000001200a14b0 000a14b0
00000000000000d0 0000000000000000 A 6 3 8
[ 9] .rela.dyn RELA 00000001200a1580 000a1580
0000000000000888 0000000000000018 A 5 0 8
[10] .rela.plt RELA 00000001200a1e08 000a1e08
0000000000001608 0000000000000018 A 5 12 8
[11] .init PROGBITS 00000001200a3410 000a3410
0000000000000038 0000000000000000 AX 0 0 8
[12] .plt PROGBITS 00000001200a3450 000a3450
00000000000003d0 0000000000000000 AX 0 0 16
[13] .text PROGBITS 00000001200a3820 000a3820
0000000000a21890 0000000000000000 AX 0 0 16
[14] .fini PROGBITS 0000000120ac50b0 00ac50b0
0000000000000028 0000000000000000 AX 0 0 8
[15] .rodata PROGBITS 0000000120ac50d8 00ac50d8
00000000000f7ba8 0000000000000000 A 0 0 8
[16] .eh_frame_hdr PROGBITS 0000000120bbcc80 00bbcc80
00000000000005dc 0000000000000000 A 0 0 4
[17] .eh_frame PROGBITS 0000000120bbd260 00bbd260
0000000000001dac 0000000000000000 A 0 0 8
[18] .gcc_except_table PROGBITS 0000000120bbf00c 00bbf00c
00000000000000f8 0000000000000000 A 0 0 4
[19] .tbss NOBITS 0000000120bc0be8 00bc0be8
0000000000000010 0000000000000000 WAT 0 0 8
[20] .init_array INIT_ARRAY 0000000120bc0be8 00bc0be8
0000000000000030 0000000000000000 WA 0 0 8
[21] .fini_array FINI_ARRAY 0000000120bc0c18 00bc0c18
0000000000000008 0000000000000000 WA 0 0 8
[22] .jcr PROGBITS 0000000120bc0c20 00bc0c20
0000000000000008 0000000000000000 WA 0 0 8
[23] .data.rel.ro PROGBITS 0000000120bc0c28 00bc0c28
000000000001b188 0000000000000000 WA 0 0 8
[24] .dynamic DYNAMIC 0000000120bdbdb0 00bdbdb0
0000000000000250 0000000000000010 WA 6 0 8
[25] .data PROGBITS 0000000120bdc000 00bdc000
0000000000008aa8 0000000000000000 WA 0 0 8
[26] .got PROGBITS 0000000120be4aa8 00be4aa8
000000000001aec8 0000000000000000 WA 0 0 8
[27] .sdata PROGBITS 0000000120bff970 00bff970
0000000000000a40 0000000000000000 WAp 0 0 8
[28] .sbss NOBITS 0000000120c003b0 00c003b0
0000000000002fd0 0000000000000000 WAp 0 0 8
[29] .bss NOBITS 0000000120c03380 00c003b0
0000000000068ac0 0000000000000000 WA 0 0 16
[30] .comment PROGBITS 0000000000000000 00c003b0
000000000000006e 0000000000000001 MS 0 0 1
[31] .debug_aranges PROGBITS 0000000000000000 00c0041e
000000000000e880 0000000000000000 0 0 1
[32] .debug_info PROGBITS 0000000000000000 00c0ec9e
0000000001df3c01 0000000000000000 0 0 1
[33] .debug_abbrev PROGBITS 0000000000000000 02a0289f
00000000000a6fba 0000000000000000 0 0 1
[34] .debug_line PROGBITS 0000000000000000 02aa9859
00000000002a8b78 0000000000000000 0 0 1
[35] .debug_frame PROGBITS 0000000000000000 02d523d8
00000000000ae558 0000000000000000 0 0 8
[36] .debug_str PROGBITS 0000000000000000 02e00930
000000000012bc32 0000000000000001 MS 0 0 1
[37] .debug_loc PROGBITS 0000000000000000 02f2c562
0000000001ae5dfb 0000000000000000 0 0 1
[38] .debug_ranges PROGBITS 0000000000000000 04a1235d
0000000000875240 0000000000000000 0 0 1
[39] .shstrtab STRTAB 0000000000000000 0528759d
0000000000000184 0000000000000000 0 0 1
[40] .symtab SYMTAB 0000000000000000 052881a8
00000000000a1160 0000000000000018 41 19147 8
[41] .strtab STRTAB 0000000000000000 05329308
00000000001045d4 0000000000000000 0 0 1
with -fasynchronous-unwind-tables:
real 138m44.140s
user 438m27.437s
sys 18m4.465s
88245562 Oct 2 22:45 cc1
106953548 Oct 2 22:45 cc1plus
readelf -S gcc/cc1
There are 42 section headers, starting at offset 0x5282398:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .interp PROGBITS 00000001200002a8 000002a8
0000000000000013 0000000000000000 A 0 0 1
[ 2] .note.ABI-tag NOTE 00000001200002bc 000002bc
0000000000000020 0000000000000000 A 0 0 4
[ 3] .hash HASH 00000001200002e0 000002e0
00000000000154d0 0000000000000008 A 5 0 8
[ 4] .gnu.hash GNU_HASH 00000001200157b0 000157b0
000000000000be78 0000000000000000 A 5 0 8
[ 5] .dynsym DYNSYM 0000000120021628 00021628
0000000000030e88 0000000000000018 A 6 1 8
[ 6] .dynstr STRTAB 00000001200524b0 000524b0
000000000004aec9 0000000000000000 A 0 0 1
[ 7] .gnu.version VERSYM 000000012009d37a 0009d37a
0000000000004136 0000000000000002 A 5 0 2
[ 8] .gnu.version_r VERNEED 00000001200a14b0 000a14b0
00000000000000d0 0000000000000000 A 6 3 8
[ 9] .rela.dyn RELA 00000001200a1580 000a1580
0000000000000888 0000000000000018 A 5 0 8
[10] .rela.plt RELA 00000001200a1e08 000a1e08
0000000000001608 0000000000000018 A 5 12 8
[11] .init PROGBITS 00000001200a3410 000a3410
0000000000000038 0000000000000000 AX 0 0 8
[12] .plt PROGBITS 00000001200a3450 000a3450
00000000000003d0 0000000000000000 AX 0 0 16
[13] .text PROGBITS 00000001200a3820 000a3820
0000000000a21890 0000000000000000 AX 0 0 16
[14] .fini PROGBITS 0000000120ac50b0 00ac50b0
0000000000000028 0000000000000000 AX 0 0 8
[15] .rodata PROGBITS 0000000120ac50d8 00ac50d8
00000000000f7ba8 0000000000000000 A 0 0 8
[16] .eh_frame_hdr PROGBITS 0000000120bbcc80 00bbcc80
000000000001a86c 0000000000000000 A 0 0 4
[17] .eh_frame PROGBITS 0000000120bd74f0 00bd74f0
000000000008b3b4 0000000000000000 A 0 0 8
[18] .gcc_except_table PROGBITS 0000000120c628a4 00c628a4
00000000000000f8 0000000000000000 A 0 0 4
[19] .tbss NOBITS 0000000120c72be8 00c62be8
0000000000000010 0000000000000000 WAT 0 0 8
[20] .init_array INIT_ARRAY 0000000120c72be8 00c62be8
0000000000000030 0000000000000000 WA 0 0 8
[21] .fini_array FINI_ARRAY 0000000120c72c18 00c62c18
0000000000000008 0000000000000000 WA 0 0 8
[22] .jcr PROGBITS 0000000120c72c20 00c62c20
0000000000000008 0000000000000000 WA 0 0 8
[23] .data.rel.ro PROGBITS 0000000120c72c28 00c62c28
000000000001b188 0000000000000000 WA 0 0 8
[24] .dynamic DYNAMIC 0000000120c8ddb0 00c7ddb0
0000000000000250 0000000000000010 WA 6 0 8
[25] .data PROGBITS 0000000120c8e000 00c7e000
0000000000008aa8 0000000000000000 WA 0 0 8
[26] .got PROGBITS 0000000120c96aa8 00c86aa8
000000000001aec8 0000000000000000 WA 0 0 8
[27] .sdata PROGBITS 0000000120cb1970 00ca1970
0000000000000a40 0000000000000000 WAp 0 0 8
[28] .sbss NOBITS 0000000120cb23b0 00ca23b0
0000000000002fd0 0000000000000000 WAp 0 0 8
[29] .bss NOBITS 0000000120cb5380 00ca23b0
0000000000068ac0 0000000000000000 WA 0 0 16
[30] .comment PROGBITS 0000000000000000 00ca23b0
000000000000006e 0000000000000001 MS 0 0 1
[31] .debug_aranges PROGBITS 0000000000000000 00ca241e
000000000000e880 0000000000000000 0 0 1
[32] .debug_info PROGBITS 0000000000000000 00cb0c9e
0000000001df3c01 0000000000000000 0 0 1
[33] .debug_abbrev PROGBITS 0000000000000000 02aa489f
00000000000a6fba 0000000000000000 0 0 1
[34] .debug_line PROGBITS 0000000000000000 02b4b859
00000000002a6660 0000000000000000 0 0 1
[35] .debug_frame PROGBITS 0000000000000000 02df1ec0
0000000000009710 0000000000000000 0 0 8
[36] .debug_str PROGBITS 0000000000000000 02dfb5d0
000000000012bc07 0000000000000001 MS 0 0 1
[37] .debug_loc PROGBITS 0000000000000000 02f271d7
0000000001ae5dfb 0000000000000000 0 0 1
[38] .debug_ranges PROGBITS 0000000000000000 04a0cfd2
0000000000875240 0000000000000000 0 0 1
[39] .shstrtab STRTAB 0000000000000000 05282212
0000000000000184 0000000000000000 0 0 1
[40] .symtab SYMTAB 0000000000000000 05282e18
00000000000a1160 0000000000000018 41 19147 8
[41] .strtab STRTAB 0000000000000000 05323f78
00000000001045c2 0000000000000000 0 0 1
2012-10-03 Uros Bizjak <[email protected]>
* configure.ac (noexception_flags): Add -fasynchronous-unwind-tables.
* configure: Regenerate.
Bootstrapped and regression tested on x86_64-pc-linux-gnu {,-m32} and
alphaev68-pc-linux-gnu.
OK for mainline?
Uros.
Index: configure
===================================================================
--- configure (revision 191991)
+++ configure (working copy)
@@ -6636,7 +6636,7 @@
# Disable exceptions and RTTI if building with g++
noexception_flags=
save_CFLAGS="$CFLAGS"
-for real_option in -fno-exceptions -fno-rtti; do
+for real_option in -fno-exceptions -fno-rtti -fasynchronous-unwind-tables; do
# Do the check with the no- prefix removed since gcc silently
# accepts any -Wno-* option on purpose
case $real_option in
Index: configure.ac
===================================================================
--- configure.ac (revision 191991)
+++ configure.ac (working copy)
@@ -365,7 +365,8 @@
# Disable exceptions and RTTI if building with g++
ACX_PROG_CC_WARNING_OPTS(
- m4_quote(m4_do([-fno-exceptions -fno-rtti])), [noexception_flags])
+ m4_quote(m4_do([-fno-exceptions -fno-rtti
-fasynchronous-unwind-tables])),
+ [noexception_flags])
# Enable expensive internal checks
is_release=
