On Mon, 24 Oct 2022, Mark Harmstone wrote:
Both current lld and the next version of ld have an option -pdb, which
creates a PDB file which Microsoft's debuggers can use. This patch adds
a -gcodeview option, which passes this to the linker.
I do intend to expand this so it also creates the .debug$S and .debug$T
sections which would make this useful - I submitted patches for this a
while back, but they need to be rewritten to parse the DWARF DIEs rather
than using debug_hooks.
Clang also has -gcodeview, but AFAICS only uses it for .debug$S and
.debug$T, and doesn't use it for linker options (though IMO it probably
should).
That's true - in Clang, this option doesn't affect linking, it only
affects code generation.
(FWIW, if I understand it correctly, Clang also does support generating
both DWARF and CodeView at the same time - I think that would require
passing something like "-g -gdwarf-4 -gcodeview" at the same time - but I
don't have experience with playing with such setups.)
Another vague oddity in how this option is handled in Clang, is that if I
only pass "-gcodeview" to the compiler, it doesn't actually generate any
debug info (it just changes preference, in case I would request debug info
separately), while one has to pass e.g. "-g -gcodeview" for it to do
what's expected. I'm not sure if this is the same with dwarf, or if
passing "-gdwarf-4" is enough for actually enabling generating dwarf debug
info too. In any case, I don't think this aspect needs to be matched
closely (unless dwarf does the same), as any existing users of PDB
generation do use "-g -gcodeview", so as long as that case works, there
shouldn't be any interop issues.
---
gcc/common.opt | 4 ++++
gcc/doc/invoke.texi | 7 +++++++
gcc/gcc.cc | 4 ++++
gcc/opts.cc | 3 +++
4 files changed, 18 insertions(+)
@@ -4608,6 +4608,10 @@ driver_handle_option (struct gcc_options *opts,
do_save = false;
break;
+ case OPT_gcodeview:
+ add_infile ("-pdb=", "*");
+ break;
Hmm, what does this end up passing to the linker in the end - does it just
pass "-pdb="? (What does the "*" parameter do here?) If that's the case -
that sounds reasonable - assuming that if a user passes an extra
-Wl,--pdb,myspecificname.pdb, that would take precedence (i.e. be passed
after the compiler's default one).
// Martin
