[llvm-dev] llvm-config-3.8.1 --cflags added -pedantic

Justin Bogner via llvm-dev llvm-dev at lists.llvm.org
Mon Aug 15 09:45:27 PDT 2016

Henning Thielemann via llvm-dev <llvm-dev at lists.llvm.org> writes:
> When switching from LLVM-3.8 to LLVM-3.8.1 (I use the Ubuntu packages)
> I got a lot of warnings when compiling my code. It seems that that
> `llvm-config --cflags` added e.g. the -pedantic flag. The pedantic
> flag seems to remain in llvm-config-3.9. I wonder whether it is the
> business of llvm-config to choose my compiler warnings. Was this
> change intended and with what reasons?

This seems kind of bad, but I don't think it's a new problem. I'm pretty
sure llvm-config --cflags has always leaked the warning flags that llvm
happened to be built with. ISTR a discussion about changing this to a
more specific set of flags to pass through a while back, but I guess it
didn't result in anything.

> Btw. the switch from llvm-3.8 to llvm-3.8.1 also removed
> include/llvm/Config/config.h without previous deprecation. I think it
> is a bad idea to do this in a bugfix release. I was always uncertain
> whether I should include config.h or llvm-config.h and it seems I
> chose the wrong one (namely config.h).

The change to stop installing the internal config.h header happened in
2014, in r210766, so I would have expected this to have been gone since
llvm 3.5 at the latest. Maybe the configure and cmake builds behaved
differently here, and the ubuntu packaging switched build systems?

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