[Bug go/27238] [gcc-11] FAIL: gdb.go/package.exp: setting breakpoint at package2.Foo

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

https://sourceware.org/bugzilla/show_bug.cgi?id=27238

--- Comment #15 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=3f577261903d4558451b005bbfee03fcdbb1d570

commit 3f577261903d4558451b005bbfee03fcdbb1d570
Author: Tom de Vries <tdevries@suse.de>
Date:   Thu Oct 5 23:22:11 2023 +0200

    [gdb/go] Handle v3 go_0 mangled prefix

    With gcc-10 we have:
    ...
    (gdb) break package2.Foo^M
    Breakpoint 2 at 0x402563: file package2.go, line 5.^M
    (gdb) PASS: gdb.go/package.exp: setting breakpoint 1
    ...
    but with gcc-11:
    ...
    gdb) break package2.Foo^M
    Function "package2.Foo" not defined.^M
    Make breakpoint pending on future shared library load? (y or [n]) n^M
    (gdb) FAIL: gdb.go/package.exp: gdb_breakpoint: set breakpoint at
package2.Foo
    ...

    In the gcc-10 case, though the exec contains dwarf, it's not used to set
the
    breakpoint (which is an independent problem, filed as PR go/30941), instead
    the minimal symbol information is used.

    The minimal symbol information changed between gcc-10 and gcc-11:
    ...
    $ nm a.out.10 | grep Foo
    000000000040370d T go.package2.Foo
    0000000000404e50 R go.package2.Foo..f
    $ nm a.out.11 | grep Foo
    0000000000403857 T go_0package2.Foo
    0000000000405030 R go_0package2.Foo..f
    ...

    A new v3 mangling scheme was used.  The mangling schemes define a separator
    character and mangling character:
    - for v2, dot is used both as separator character and mangling character,
and
    - for v3, dot is used as separator character and underscore as mangling
      character.

    For more details, see [1] and [2].

    In v3, "_0" demangles to ".". [ See gcc commit a01dda3c23b ("compiler,
libgo:
    change mangling scheme"), function Special_char_code::Special_char_code. ]

    Handle the new go_0 prefix in unpack_mangled_go_symbol, which fixes the
    test-case.

    Note that this doesn't fix this regression:
    ...
    $ gccgo-10 package2.go -c -g0
    $ gccgo-10 package1.go package2.o -g0
    $ gdb -q -batch a.out -ex "break go.package2.Foo"
    Breakpoint 1 at 0x40370d
    $ gccgo-11 package2.go -c -g0
    $ gccgo-11 package1.go package2.o -g0
    $ gdb -q -batch a.out -ex "break go.package2.Foo"
    Function "go.package2.Foo" not defined.
    ...

    With gcc-10, we set a breakpoint on the mangled minimal symbol.  That
    one has simply changed for gcc-11, so it's equivalent to using:
    ...
    $ gdb -q -batch a.out -ex "break go_0package2.Foo"
    Breakpoint 1 at 0x403857
    ...
    which does work.

    Tested on x86_64-linux:
    - openSUSE Leap 15.4, using gccgo-7,
    - openSUSE Tumbleweed, using gccgo-13.

    PR go/27238
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27238

    [1] https://go-review.googlesource.com/c/gofrontend/+/271726
    [2] https://github.com/golang/go/issues/41862#issuecomment-707244103

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