[NFC][cmake] Build fix in tools/llvm-config/CMakeLists.txt

[GBuella]

Summary

To avoid the following error message (using cmake version 3.13.4) :

CMake Error at tools/llvm-config/CMakeLists.txt:37 (string):
Syntax error in cmake code  when parsing string-std=[^ ]\+Invalid escape sequence \+

[tstellar]

Has this change been tested with newer older versions of cmake too? Was there a release note from CMake that announced the deprecation of this kind of escape sequence?

[mgorny]

LGTM. According to CMake manual, plain + is the only correct form and if \+ worked at all, it was probably only by accident.

That said, you'll need to update the patch since third match was added below.

tools/llvm-config/CMakeLists.txt

 # Fetch target specific compile options, e.g. RTTI option
 get_property(COMPILE_FLAGS TARGET llvm-config PROPERTY COMPILE_FLAGS)
 
 # The language standard potentially affects the ABI/API of LLVM, so we want
 # to make sure it is reported by llvm-config.
 # NOTE: We don't want to start extracting any random C/CXX flags that the
 # user may add that could affect the ABI.  We only want to extract flags
 # that have been added by the LLVM build system.
-string(REGEX MATCH "-std=[^ ]\+" LLVM_CXX_STD_FLAG ${CMAKE_CXX_FLAGS})
-string(REGEX MATCH "-std=[^ ]\+" LLVM_C_STD_FLAG ${CMAKE_C_FLAGS})
+string(REGEX MATCH "-std=[^ ]+" LLVM_CXX_STD_FLAG ${CMAKE_CXX_FLAGS})
+string(REGEX MATCH "-std=[^ ]+" LLVM_C_STD_FLAG ${CMAKE_C_FLAGS})
 
 # Use configure_file to create BuildVariables.inc.
 set(LLVM_SRC_ROOT ${LLVM_MAIN_SRC_DIR})
 set(LLVM_OBJ_ROOT ${LLVM_BINARY_DIR})
 set(LLVM_CPPFLAGS "${LLVM_DEFINITIONS}")
 set(LLVM_CFLAGS "${LLVM_C_STD_FLAG} ${LLVM_DEFINITIONS}")
 set(LLVM_CXXFLAGS "${LLVM_CXX_STD_FLAG} ${COMPILE_FLAGS} ${LLVM_DEFINITIONS}")
 set(LLVM_BUILD_SYSTEM cmake)