From: "Hans-Bernhard Bröker" <HBBroeker@t-online.de>
To: cygwin@cygwin.com
Subject: Re: Defaulting to stabs debug output from AS Cygwin64
Date: Tue, 15 May 2018 21:18:00 -0000 [thread overview]
Message-ID: <068140eb-e8bf-c5a9-41e5-36120983cc9b@t-online.de> (raw)
In-Reply-To: <CAOC2fq-fhFXBPBVFWNQpqUeKZf-2KFowUeAzv9xkBSDQud=1zg@mail.gmail.com>
Am 15.05.2018 um 19:17 schrieb Michael Enright:
> The GCC driver uses -gdwarf2 if you do 'gcc -g' on a .s file. Using
> -gdwarf2 with assembly code manually or through gcc is successful in
> producing a Cygwin64 executable that Cygwin64 GDB can work with. This
> combination of circumstances led me to wonder how stabs was chosen for
> Cygwin64.
Basically because it was not chosen. It's not even actually supported,
as evidenced by those relocation failures: not how those occurred in the
.stab section.
"The" default of Cygwin is whatever the compiler uses, i.e. Dwarf2, and
was indeed chosen, because none of the older formats stand a chance of
really handling the amount and complexity of debug information needed
for modern-day C++.
On to of that, making '-gdwarf-2' the default -g mode for 'as' would be
an exercise in futility anyway, because that option is essentially a
no-op. That's because Dwarf-2 debug information is _not_ actually
created by the -g flag to begin with: it's spelled out by the compiler
as reams of data and reloc statements, to go into specially named
sections like '.debug_info'. GCC doesn't even pass any '-g' flag to the
assembler in its default -gdwarf-2 mode.
It makes sense that "as -g" equals "as -gstabs" because unlike the other
ones, that one at least does something: it causes .def pseudo-ops to put
data into the .stab section, which also is automatically created by that
option.
In a nutshell: you don't want to use either of "as -g" or "as -gstabs"
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prev parent reply other threads:[~2018-05-15 20:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-15 12:49 Michael Enright
2018-05-15 13:18 ` cyg Simple
2018-05-15 17:41 ` Michael Enright
2018-05-15 21:18 ` Hans-Bernhard Bröker [this message]
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