[Bug breakpoints/26546] [pie] Setting breakpoint on missing label sets breakpoint at offset 0 in NULL section

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=26546

--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom de Vries <vries@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=8f5c6526ebbd8b5749dd2f348796b53f3e2b25ee

commit 8f5c6526ebbd8b5749dd2f348796b53f3e2b25ee
Author: Tom de Vries <tdevries@suse.de>
Date:   Thu Sep 3 12:30:10 2020 +0200

    [gdb/breakpoint, PIE] Handle setting breakpoint on label without address

    When adding:
    ...
    if ![runto_main] then {
        fail "can't run to main"
        return 0
    }
    ...
    to test-case gdb.base/label-without-address.exp and running it with target
    board unix/-fPIE/-pie, we run into:
    ...
    (gdb) break main:L1^M
    Breakpoint 2 at 0x555555554000: file label-without-address.c, line 22.^M
    ...
    That is, for a label with optimized-out address, we set a breakpoint at the
    relocation base.

    The root cause is that the dwarf reader, despite finding that attribute
    DW_AT_low_pc is missing, still tags the L1 symbol as having LOC_LABEL,
which
    means it has a valid address, which defaults to 0.

    Fix this by instead tagging the L1 symbol with LOC_OPTIMIZED_OUT.

    Tested on x86_64-linux.

    gdb/ChangeLog:

    2020-09-03  Tom de Vries  <tdevries@suse.de>

            PR breakpoint/26546
            * dwarf2/read.c (new_symbol): Tag label symbol without DW_AT_low_pc
as
            LOC_OPTIMIZED_OUT instead of LOC_LABEL.

    gdb/testsuite/ChangeLog:

    2020-09-03  Tom de Vries  <tdevries@suse.de>

            PR breakpoint/26546
            * gdb.base/label-without-address.exp: Runto main first.

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