Search for llvm-config in LLDB_PATH_TO_LLVM_BUILD first

[tfiala]

Summary

If LLDB_PATH_TO_LLVM_BUILD is present, search for llvm-config there first before looking in CMake or system paths.

(The patch is a modified fix from @tfiala)

[tfiala]

LGTM.

[tfiala]

(It would be good to wait for feedback from the others, though).

[tfiala]

cmake/modules/LLDBStandalone.cmake

20

One question here would be what happens if FIND_PATHS stays "". Does find_program deal with an empty HINTS? If not, the HINTS clause itself might need to be conditionalized.

[beanz]

LLDB_PATH_TO_LLVM_BUILD is a swift-ism that doesn't match LLVM's CMake conventions. In LLVM we don't pass in the path to build directories, instead we pass in LLVM_CONFIG to standalone builds, and we derive the build directory from the output of llvm-config.

Passing in LLVM_CONFIG is more flexible, robust, and consistent with how other LLVM subprojects work, and I see no reason to change that convention.

[mgorny]

I agree. Don't introduce redundant variables when the same result can be achieved using existing means.

(note that find_program makes LLVM_CONFIG a cache variable implicity, so you don't need to have any explicit support for altering it)

[labath]

+cc: lldb standalone users

I'll defer to @beanz on this.

[krytarowski]

I think it's possible to specify -DLLVM_CONFIG:PATH option, if that does the job.

[tfiala]

@beanz and I discussed. This isn't needed here at all. The issue is entirely in the current manifestation of the GitHub side of swift-lldb.

Closing this out, we'll resolve in GitHub.

[vivkong]

This is not required anymore and it can be closed. Thanks.

[tfiala]

I'm at a loss for the workflow to close this. I originally commandeered it to do an abort on it, but that didn't work. I'm going to abandon it, and see if I can kill it then.

cmake/modules/LLDBStandalone.cmake

 
   # Rely on llvm-config.
   set(CONFIG_OUTPUT)
-  find_program(LLVM_CONFIG "llvm-config")
+  set(FIND_PATHS "")
+  if (LLDB_PATH_TO_LLVM_BUILD)
+    set(FIND_PATHS "${LLDB_PATH_TO_LLVM_BUILD}/bin")
+  endif()
+  find_program(LLVM_CONFIG "llvm-config"
+    HINTS ${FIND_PATHS})
   if(LLVM_CONFIG)
     message(STATUS "Found LLVM_CONFIG as ${LLVM_CONFIG}")
     set(CONFIG_COMMAND ${LLVM_CONFIG}