Mail Archives: djgpp/2015/06/09/18:30:05
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| Newsgroups: | comp.os.msdos.djgpp
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| Date: | Tue, 9 Jun 2015 15:17:08 -0700 (PDT)
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| Subject: | Re: DJGPP port of binutils broken due to 64 bit cygwin fix.
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| From: | "Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de)" <djgpp AT delorie DOT com>
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On Thursday, June 4, 2015 at 1:55:25 PM UTC+2, Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) wrote:
> It turns out that the DJGPP (aka go32) port of binutils has been broken since
> binutils 2.25 has been released. The DJGPP port of binutils 2.24 and previous
> versions works flawlessly. Please note that there is nothing particular about
> this port. It is simply an absolute generic 32-bit coff system that uses DWARF2.
>
> The breakage can be demonstrated by compiling a simple hello-world program with
> the flags -g2 -O0. If one tries to step through the code using the DJGPP port
> of gdb then the following output will be displayed:
>
>
> ----------------------- start of gdb output -------------------------------
>
> C:\tmp\5>gdb a.exe
> GNU gdb (GDB) 7.7.1
> Copyright (C) 2014 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law. Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "--host=i786-pc-msdosdjgpp --target=djgpp".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>.
> Find the GDB manual and other documentation resources online at:
> <http://www.gnu.org/software/gdb/documentation/>.
> For help, type "help".
> Type "apropos word" to search for commands related to "word"...
> Reading symbols from a.exe...done.
> (gdb) b main
> Breakpoint 1 at 0x1f6a
> (gdb) r
> Starting program: c:/tmp/5/a.exe
>
> Breakpoint 1, 0x00001f6a in main ()
> (gdb) s
> Single stepping until exit from function main,
> which has no line number information.
> hello world
> 0x00004504 in __crt1_startup ()
> (gdb)
>
> ----------------------- end of gdb output -------------------------------
>
>
>
>
> If one uses objdump to inspect the binary, using --dwarf, an output like this
> will be produced:
>
>
>
> ----------------------- start of objdump output -------------------------------
>
>
> a.exe: file format coff-go32-exe
>
> Contents of the .debug_aranges section:
>
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: Bogus end-of-siblings marker detected at offset b1 in .debug_info section
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: Bogus end-of-siblings marker detected at offset b2 in .debug_info section
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: DIE at offset b3 refers to abbreviation number 3986 which does not exist
> Length: 28
> Version: 2
> Offset into .debug_info: 0x0
> Pointer Size: 4
> Segment Size: 0
> [snip, truncated by me]
>
> Contents of the .debug_info section:
>
> Compilation Unit @ offset 0x0:
> Length: 0x46 (32-bit)
> Version: 2
> Abbrev Offset: 0x0
> Pointer Size: 4
> <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
> <c> DW_AT_stmt_list : 0x0
> <10> DW_AT_low_pc : 0x1a10
> <14> DW_AT_high_pc : 0x1f27
> <18> DW_AT_name : crt0.S
> <1f> DW_AT_comp_dir : c:/djgpp-O0-g2/src/libc/crt0
> <3c> DW_AT_producer : GNU AS 2.25
> <48> DW_AT_language : 32769 (MIPS assembler)
> Compilation Unit @ offset 0x4a:
> Length: 0x19f (32-bit)
> Version: 2
> Abbrev Offset: 0x0
> Pointer Size: 4
> <0><55>: Abbrev Number: 1 (DW_TAG_compile_unit)
> <56> DW_AT_stmt_list : 0x20554e47
> <5a> DW_AT_low_pc : 0x2e342043
> <5e> DW_AT_high_pc : 0x20322e39
> <62> DW_AT_name : -fpreprocessed -mtune=pentium -march=pentium -g3 -gdwarf-2 -O0
> <a1> DW_AT_comp_dir : a.c
> <a6> DW_AT_producer : c:/tmp/5
> <af> DW_AT_language : 7984 (Unknown: 1f30)
> <0><b1>: Abbrev Number: 0
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: Bogus end-of-siblings marker detected at offset b1 in .debug_info section
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: Further warnings about bogus end-of-sibling markers suppressed
> <-1><b2>: Abbrev Number: 0
> <-2><b3>: Abbrev Number: 3986
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: DIE at offset b3 refers to abbreviation number 3986 which does not exist
> Contents of the .debug_abbrev section:
> [snip, truncated by me]
>
>
> Offset: 0x6e0a
> Length: 78
> DWARF Version: 2
> Prologue Length: 58
> Minimum Instruction Length: 1
> Initial value of 'is_stmt': 1
> Line Base: -5
> Line Range: 14
> Opcode Base: 13
>
> [snip, truncated by me]
>
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: Unable to load/parse the .debug_info section, so cannot interpret the .debug_loc section.
> C:\DJGPP-2.04\BIN/objdump.exe: Warning: Unable to load/parse the .debug_info section, so cannot interpret the .debug_ranges section.
> Contents of the .debug_macro section:
> [snip, truncated by me]
>
> ----------------------- end of objdump output -------------------------------
>
>
>
> Please note that I have intentionally truncated a lot of the output produced by
> objdump. But I think that everyone can see that the debug info stored in the
> file has been corrupted.
>
>
> An inspection of the repository of binutils, specially a comparision between
> the binutil-2_25-branch/master and the binutil-2_24-branch reveals that the
> function _bfd_coff_generic_relocate_section in bfd/cofflink.c has been modified
> by the following patch (55bfc9ac025c1c9cd1ad5422829b3dc70f357a79):
>
> Autor: Nick Clifton <nickc AT redhat DOT com> 2014-03-26 17:16:20
> Eintragender: Nick Clifton <nickc AT redhat DOT com> 2014-03-26 17:16:20
> Eltern: 318d3177f7d67dac94baa07aab04192fc7bcba49 (Remove VAR_DOMAIN/STRUCT_DOMAIN ambiguity from ada-tasks.c.)
> Kind: b3fe4307a625457c6953fce27bbbfc4c90e38e9d (Add support for %hi8, %hi16 and %lo16 being used when relocation are necessary.)
> Zweig: binutils-2_25-branch, master, remotes/origin/binutils-2_25-branch and many more (44)
> Folgt auf: binu_ss_19990502, readline_4_0
> Vorgänger von: binutils-2_25, gdb-7.8-release, gdb-7.9.0-release, hjl/linux/release/2.24.51.0.4
>
> This fixes a problem for 64-bit Cygwin, where building some packages can
> produce spurious errors about truncated relocations. The relocations are
> only truncated because they are being made against sections which are going
> to be discarded so that base address is zero instead of the expected 64-bit
> base value.
>
> * cofflink.c (_bfd_coff_generic_relocate_section): Skip
> relocations in discarded sections.
>
>
>
>
>
> @@ -3059,6 +3059,11 @@ _bfd_coff_generic_relocate_section (bfd *output_bfd,
> else
> {
> sec = sections[symndx];
> +
> + /* If the output section has been discarded then ignore this reloc. */
> + if (sec->output_section->vma == 0)
> + continue;
> +
> val = (sec->output_section->vma
> + sec->output_offset
> + sym->n_value);
>
>
>
>
> Because the DJGPP port is an absolute _generic_ 32-bit coff system I suspect
> that the patch above has probably brocken almost every coff 32-bit systems
> except for pe-coff may be.
>
>
> I have solved the issue for myself by this change:
>
>
> diff --git a/bfd/cofflink.c b/bfd/cofflink.c
> index ef9e362..162d832 100644
> --- a/bfd/cofflink.c
> +++ b/bfd/cofflink.c
> @@ -2979,9 +2979,13 @@ _bfd_coff_generic_relocate_section (bfd *output_bfd,
> {
> sec = sections[symndx];
>
> +
> + /* Only if not a 32-bit system. */
> +#ifndef __DJGPP__
> /* If the output section has been discarded then ignore this reloc. */
> if (sec->output_section->vma == 0)
> continue;
> +#endif
>
> val = (sec->output_section->vma
> + sec->output_offset
>
>
> Of course this should not be fixed in this way. Unfortunately my bfd skills
> are to limited to disign a solution that would identify that coff version that
> requires the ignoring of the discarded relocations and those versions that do
> not. If someone creates a solution for this issue and need assitance to test
> it, please contact me.
>
>
> Regards,
> Juan M. Guerrero
OFYI, today I got response from Alan Modra concerning this issue. Please, see:
<https://sourceware.org/ml/binutils/2015-06/msg00111.html>
It may be of interset for some one else really familiar with COFF and bfd and the DJGPP port of binutils. I post this here because I have noted that the mail has been cc'ed to djgpp AT delorie DOT com this morning (more than 12 hs ago) but it has still not appeared here.
I will try the patch propossed by Alan Modra and answer at binutils AT sourceware DOT org.
Regards,
Juan M. Guerrero
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