While investigating some issues in the libffi tests, I came across some
cases where errors are caused by DejaGnu's get_multilibs function. For
some unclear reason, this only seems to get invoked for C++ tests, but
when it is, there can be a problem, because under some circumstances it
invokes the compiler with the -dumpspecs option, which is a gcc-only
option that clang chokes on. Even when it's using gcc, it bloats the
logfile with the verbose -dumpspecs output, in order to determine
something of highly questionable value.
I traced the results of get_multilibs (as used by the libffi tests) in
many macOS versions, and even the "successful" cases seem to have
questionably useful results:
10.4: /usr/.
10.5: /usr/.
10.6 (x86_64): /usr/x86_64
10.6 (i386): /usr/.
10.7: /usr/llvm-gcc-4.2/bin/../x86_64
10.8: ./x86_64
10.9: ./x86_64
10.10: (fails)
10.11: (fails)
10.12: (fails)
10.13: (fails)
10.14: ./.
10.15: ./.
The "/usr/." result returned on 10.4, 10.5, and 32-bit 10.6 is the same as
what I see on Ubuntu 14.04, CentOS 7, and Fedora 25, though it's not clear
to me what it's supposed to represent.
Also note that when I build and test a 32-bit version of libffi on 10.9,
the get_multilibs result is still "./x86_64".
Since get_multilibs already has code to return an empty string in the
"remote" case (where it assumes this function won't work), I just added
code to unix.exp to set multitop to "" for all "darwin" targets, thereby
short-circuiting almost all og get_multilibs. That certainly fixes the
problem with the libffi tests, and doesn't change any non-Mac behavior,
though I don't know if that's the ideal fix. The whole get_mutilibs
function looks pretty ugly anyway, and it's generally recognized that
relying on -dumpspecs is a bad idea.
I primarily tested my patch against the 1.6.2 release, since the current
master won't install from a non-git directory, and also has multiple
failures in its own tests (even on Linux). The patch is nearly identical
between the 1.6.2 and master cases, anyway.
I can send the current patch, either as a bare email or as an attachment.
AFAIK, Savannah doesn't have the pull request / merge request concept.
Fred Wright
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