Re: [doc patch] compile: missing bits [Re: [PATCH v2 7/9] compile: New 'compile print']

Jan Kratochvil
2015-04-10T08:09:47Z

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On Thu, 09 Apr 2015 20:12:21 +0200, Eli Zaretskii wrote:
> > +@value{NGCC} (since version 4.7) stores the options used for compilation
> > +into @code{DW_AT_producer} part of DWARF debugging information according
> > +to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
> > +explicitly specify @code{-g} during inferior compilation otherwise
> > +@value{NGCC} produces no DWARF.
>
> Hmm... Are you sure -g always produces DWARF? Maybe we should say
> that for targets where DWARF is not the default, -gdwarf-N should be
> used, and also that -gstabs etc. should _not_ be used?

While you are technically right I do not think it is appropriate to mention it
that way.

When some platform is still using -gstabs by default (is there any?) there are
probably some serious reasons for it - such as some old debugging / crash
analysing tools incompatible with DWARF. Using -gdwarf-X may do more harm
than good there IMO; unless one really knows what s/he is doing and then one
does not need to read this doc.

I have just added:
This feature is only relevant for
platforms where @code{-g} produces DWARF by default, otherwise one may
try to enforce DWARF by using @code{-gdwarf-4}.

> > +Specifically @code{PATH} is searched for binaries matching regular expression
> > +@code{@var{ARCH}(-[^-]*)?-@var{OS}-gcc} according to the inferior target being
> > +debugged. @code{@var{ARCH}} is processor name - multiarch is supported,
[...]
> > +for pattern @code{s390x?}. @code{OS} is currently supported only for
> > ^^^^^^^^^
>
> @var{os}.

Not sure if @code{@var{os}} is the same as @var{os}, used only @var{os}.

Thanks,
Jan

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gdb/doc/
2015-04-10 Jan Kratochvil <jan.kratochvil@redhat.com>
Eli Zaretskii <eliz@gnu.org>

* gdb.texinfo (Compiling and Injecting Code): Describe set debug
compile, show debug compile. New subsection Compilation options for
the compile command. New subsection Compiler search for the compile
command.

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index d794893..419439a 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -17223,6 +17223,66 @@ compile file /home/user/example.c
@end smallexample
@end table

+@noindent
+The process of compiling and injecting the code can be inspected using:
+
+@table @code
+@anchor{set debug compile}
+@item set debug compile
+@cindex compile command debugging info
+Turns on or off display of @value{GDBN} process of compiling and
+injecting the code. The default is off.
+
+@item show debug compile
+Displays the current state of displaying @value{GDBN} process of
+compiling and injecting the code.
+@end table
+
+@subsection Compilation options for the @code{compile} command
+
+@value{GDBN} needs to specify the right compilation options for the code
+to be injected, in part to make its ABI compatible with the inferior
+and in part to make the injected code compatible with @value{GDBN}'s
+injecting process.
+
+@noindent
+The options used, in increasing precedence:
+
+@table @asis
+@item target architecture and OS options (@code{gdbarch})
+These options depend on target processor type and target operating
+system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
+(@code{-m64}) compilation option.
+
+@item compilation options recorded in the target
+@value{NGCC} (since version 4.7) stores the options used for compilation
+into @code{DW_AT_producer} part of DWARF debugging information according
+to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
+explicitly specify @code{-g} during inferior compilation otherwise
+@value{NGCC} produces no DWARF. This feature is only relevant for
+platforms where @code{-g} produces DWARF by default, otherwise one may
+try to enforce DWARF by using @code{-gdwarf-4}.
+
+@item compilation options set by @code{set compile-args}
+@end table
+
+@noindent
+You can override compilation options using the following command:
+
+@table @code
+@item set compile-args
+@cindex compile command options override
+Set compilation options used for compiling and injecting code with the
+@code{compile} commands. These options override any conflicting ones
+from the target architecture and/or options stored during inferior
+compilation.
+
+@item show compile-args
+Displays the current state of compilation options override.
+This does not show all the options actually used during compilation,
+use @ref{set debug compile} for that.
+@end table
+
@subsection Caveats when using the @code{compile} command

There are a few caveats to keep in mind when using the @code{compile}
@@ -17380,6 +17440,24 @@ Access to those variables will generate a compiler error which @value{GDBN}
will print to the console.
@end table

+@subsection Compiler search for the @code{compile} command
+
+@value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
+may not be obvious for remote targets of different architecture than where
+@value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
+shell that executed @value{GDBN}, not the one set by @value{GDBN}
+command @code{set environment}). @xref{Environment}. @code{PATH} on
+@value{GDBN} host is searched for @value{NGCC} binary matching the
+target architecture and operating system.
+
+Specifically @code{PATH} is searched for binaries matching regular expression
+@code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
+debugged. @var{arch} is processor name --- multiarch is supported, so for
+example both @code{i386} and @code{x86_64} targets look for pattern
+@code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
+for pattern @code{s390x?}. @var{os} is currently supported only for
+pattern @code{linux(-gnu)?}.
+
@node GDB Files
@chapter @value{GDBN} Files