PATCH: fix collect2 handling of --demangle and --no-demangle

Sandra Loosemore
Sat Jun 18 00:20:00 GMT 2011

We had a bug report from a customer that the linker was ignoring the 
--demangle and --no-demangle options when generating map files. 
Moreover, it was failing in a host-dependent way; on Windows hosts, it 
was always emitting demangled names in the map file, while on Linux 
hosts, it never did.  Moreover, on Windows hosts it also ignored the 
setting of the COLLECT_NO_DEMANGLE environment variable.

This turns out to be a problem in collect2, or actually, three problems:

(1) By default, collect2 is configured to filter out --demangle and 
--no-demangle from the linker options, and it tries to do demangling on 
symbol names in stdout and stderr itself instead.  But, it is too stupid 
to know about the map file.

(2) Collect2 is trying to set COLLECT_NO_DEMANGLE to disable demangling 
in ld, but in a nonportable way that causes it to be always unset 
instead on Windows.

(3) If you configure with --with-demangler-in-ld to try to disable the 
collect2 demangling, there's another bug that causes it to ignore any 
explicit --demangle or --no-demangle options and only pay attention to 
whether or not COLLECT_NO_DEMANGLE is set.

The attached patch addresses all three problems:

(1) I've flipped the default to --with-demangler-in-ld=yes.  Note that already takes care not to let this percolate through to 
collect2 without verifying that the linker is GNU ld and that it is a 
version that supports --demangle.  Perhaps back in 2004 when this option 
was first added, the ld demangling support was deemed too experimental 
to make it the default, but that's surely not the case any more.  Also, 
since this has been broken since 2004, I'm not sure there's much reason 
to be concerned with backwards compatibility, here....

(2) I fixed the COLLECT_NO_DEMANGLE environment variable setting recipe.

(3) I simplified the argument processing for --demangle and 
--no-demangle to pass them straight through to the linker when 
HAVE_LD_DEMANGLE is defined.

OK to commit?


2011-06-17  Sandra Loosemore  <>

	* (demangler_in_ld): Default to yes.
	* configure: Regenerated.
	* collect2.c (main): When HAVE_LD_DEMANGLE is defined, don't
	mess with COLLECT_NO_DEMANGLE, and just pass --demangle and
	--no-demangle options straight through to ld.  When
	HAVE_LD_DEMANGLE is not defined, set COLLECT_NO_DEMANGLE in a
	way that has the intended effect on Windows.
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