Re: [PATCH] gnu: Add LDFLAGS=-lpthread to configure-flags where needed.

[John Darrington <john@darrington.wattle.id.au>]

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On Tue, Mar 21, 2017 at 12:29:05PM +0100, Danny Milosavljevic wrote:
     Hi John,
     
     thanks for looking into the problem.
     
     On Tue, 21 Mar 2017 02:22:11 +0100
     John Darrington <john@darrington.wattle.id.au> wrote:
     > +   (arguments `(#:configure-flags '("LDFLAGS=-lpthread")))
     
     Hmm, that seems to be a very unsafe thing to do.

I was afraid you might say that.
     
     In order to actually use pthread, one has to switch gcc into pthread mode (which influences how it handles variables etc).
     But just passing "-lpthread" to the linker does no such things and will only make it link - with the wrong actual instructions in the object files!

It used to work.   Only recently has it stopped working.
So that would seem to confirm to me that a version of gcc (or some other part of
the tool chain) recently checked into core-updates might have been misconfigured.
Is it possible that somehow pthread mode has been inadvertently switched on?
     
     
     It would be better to check out the object files (with objdump -r or objdump -t) and find out where the symbol is listed as undefined ("U"). Then check the associated source file whether it actually intended to use pthread.

I'm not familiar enough with the internals to know exactly which source file 
would be involved.  But the error message clearly says to relink libpng and libfontconfig 
using -lpthread.  I just did as told.

J'

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