Bug 452125 - Specifying LLVM_DIR causes Clang not to be found.
Summary: Specifying LLVM_DIR causes Clang not to be found.
Status: REPORTED
Alias: None
Product: kdevelop
Classification: Applications
Component: Build tools: CMake (show other bugs)
Version: git master
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: kdevelop-bugs-null
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2022-03-31 20:13 UTC by bungeman
Modified: 2022-03-31 20:13 UTC (History)
0 users

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Description bungeman 2022-03-31 20:13:56 UTC 
SUMMARY
I am on a system where clang-12 is the default but wish to build KDevelop against clang-13. I can install clang-13 and its dev packages, and set `cmake-options -DLLVM_DIR=/usr/lib/llvm-13` in my `~/.kdesrc-buildrc`. This allows llvm-13 to be found, but the cmake build steps fail to find the clang-13 libraries. The issue appears to be that in `cmake/modules/FindClang.cmake` if `LLVM_DIR` is set `find_package(LLVM ${version})` is not executed at all, which means that none of its side effects are made available (like setting (LLVM_FOUND, LLVM_LIBRARY_DIRS, etc). Simply removing `LLVM_DIR OR ` from this file allows the correct clang-13 libraries to be found and the build succeeds.


STEPS TO REPRODUCE
1. Set `cmake-options -DLLVM_DIR=/usr/lib/llvm-13` in `~/.kdesrc-buildrc`, or otherwise get LLVM_DIR to CMake.
2. Run CMake.

OBSERVED RESULT
CMake finds LLVM fine, but then fails to find Clang libraries.

EXPECTED RESULT
CMake should find the Clang libraries.