Objdump can't parse our Linux debug information

[laanwj]

Upstream issue: https://sourceware.org/bugzilla/show_bug.cgi?id=31692

The debug information in the shipped .dbg artifacts seems to be unusable for objdump. The .debug_info section is corrupt:

$ tar -zxvf bitcoin-27.0-x86_64-linux-gnu-debug.tar.gz
$ objdump -Wi bitcoin-27.0/bin/bitcoin-cli.dbg

Section '.debug_info' has an invalid size: 0.

bitcoin-27.0/bin/bitcoin-cli.dbg:     file format elf64-x86-64

Section '.debug_info' has an invalid size: 0.

i've checked various Linux architectures (at least x86_64, ARM, RISC-V) and the same issue exists there. Interestingly, the Windows build is unaffected. Maybe because of a different gcc/binutils? Builds outside guix seem unaffected.

My first thought is that something goes wrong while splitting the debug symbols. However, the unsplitted binaries suffer from the same problem:

$ objdump -Wi guix-build-27.0/distsrc-27.0-x86_64-linux-gnu/src/bitcoind

Section '.debug_info' has an invalid size: 0

This issue affects at least release 27.0 and current master.

Edit: Looks like there is a .debug_info section in the files. objdump -s -j .debug_info bitcoin-27.0/bin/bitcoind.dbg shows contents, so it's not really size 0. But it can't be parsed somehow.

[laanwj]

Okay, may be a objdump bug actually?

readelf -wi (which should be equivalent to objdump -Wi) parses the same section fine. So does gdb it seems?

(FWIW i did try various versions of objdump before reporting this)

[laanwj]

Closing for now.

edit: It's this objdump bug in dealing with compressed debug info sections: https://sourceware.org/bugzilla/show_bug.cgi?id=24319
which was supposedly fixed but... sigh

[laanwj]

Reopening with more accurate title (phew).

Filed upstream issue: https://sourceware.org/bugzilla/show_bug.cgi?id=31692

[fanquake]

Interestingly, the Windows build is unaffected. Maybe because of a different gcc/binutils?

This is probably because the Windows Binutils is configured without support for compressed debug sections, as it was, iirc, causing other windows build issues.

[laanwj]

This is probably because the Windows Binutils is configured without support for compressed debug sections, as it was, iirc, causing other windows build issues.

Right, that makes sense. DWARF in PE binaires is a quite peculiar concept in the first place--heck, GNU even has its own way to encode the long section names needed: lief-project/LIEF#1043. i'm not surprised it's not set up to handle compressed sections.

[laanwj]

This was already solved upstream!

Diff: https://sourceware.org/git/?p=binutils-gdb.git;a=blobdiff;f=binutils/objdump.c;h=3d70df470f290f7e4dc46cf80bc075f3015e6c14;hp=5acaa54929dbd4bbe37d7a2195ca698bfca603d0;hb=635d05b88f4823f46ef1ddbb3d438db16c0f6e71;hpb=5ce0e02478cc79a260c7e29822450284a32b9b12

i expect this will land in binutils 2.43. No need to keep this issue open.