[LLVMdev] Linking Clang with an optional external library

[Ryan Govostes]

Hi,

I'd like to link Clang against the STP theorem prover. Since Clang is built by the LLVM build system, I hope this is the correct place to ask for advice.

The attached patch allows me to pass `configure` a --with-stp option and provide a path to the install prefix for STP. However, I am not familiar with autoconf, so I am not confident that my changes are the correct way to do this. I would appreciate feedback on the proposed change.

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Besides the configure.ac changes in the patch, I am unsure of the appropriate place to add the linker flag. Currently I am simply appending to LDFLAGS in Clang's tools/driver/Makefile:

+ifdef STP_INSTALL_PREFIX
+LDFLAGS += -L$(STP_INSTALL_PREFIX)/lib -lstp
+endif


To support CMake builds as well, is it sufficient to add the following to config.h.cmake, and expect the user to pass -DWITH_STP_PREFIX= if they would like to use this feature?

#cmakedefine STP_C_INTERFACE ${WITH_STP_PREFIX}/include/stp/c_interface.h


One potential issue I noticed in writing this patch is that LLVM's config.h and Clang's config.h are both #include-guarded by the CONFIG_H macro, and consequently both cannot be included from the same source file. Perhaps these should be changed to LLVM_CONFIG_H and CLANG_CONFIG_H, respectively?


Thanks,
Ryan