[LLVM] Support histedit.h and libedit.a in non-standard locations

[RVP]

Summary

When histedit.h and libedit.a are in non-standard locations which is not
uncommon, cmake does not automatically configure LLVM to build the line
editor. But completion and history provided by LineEditor are very useful in
clang-query.

To use this -DLLVM_ENABLE_LIBEDIT=ON must be specified along with the location
of libedit.a and histedit.h in -DCMAKE_LIBRARY_PATH=... and
-DCMAKE_INCLUDE_PATH=... respectively. Alternatively, the full path to these
files can specified using -DLIBEDIT_LIBRARY=... and -DHISTEDIT_FILE=...
respectively

There are some instances such as when using ASan, building with libedit is
skipped. That will continue to be the case.

[RVP]

This seems to cause a build failure.

ld.lld: error: undefined symbol: strvis
>>> referenced by hist.o:(hist_command) in archive /usr/lib/x86_64-linux-gnu/libedit.a
>>> referenced by history.o:(history_save_fp) in archive /usr/lib/x86_64-linux-gnu/libedit.a
>>> referenced by historyn.o:(history_save_fp) in archive /usr/lib/x86_64-linux-gnu/libedit.a
 
ld.lld: error: undefined symbol: strlcpy
>>> referenced by terminal.o:(terminal_settc) in archive /usr/lib/x86_64-linux-gnu/libedit.a
>>> referenced by terminal.o:(terminal_settc) in archive /usr/lib/x86_64-linux-gnu/libedit.a
>>> referenced by tty.o:(tty_stty) in archive /usr/lib/x86_64-linux-gnu/libedit.a
>>> did you mean: strncpy
>>> defined in: /lib/x86_64-linux-gnu/libc.so.6

Closing this for now as it seems this may need further work.

[RVP]

Abandoning it. Will submit a new patch later.

llvm/cmake/config-ix.cmake

 check_include_file(termios.h HAVE_TERMIOS_H)
 check_include_file(unistd.h HAVE_UNISTD_H)
 check_include_file(valgrind/valgrind.h HAVE_VALGRIND_VALGRIND_H)
 check_include_file(fenv.h HAVE_FENV_H)
 check_symbol_exists(FE_ALL_EXCEPT "fenv.h" HAVE_DECL_FE_ALL_EXCEPT)
 check_symbol_exists(FE_INEXACT "fenv.h" HAVE_DECL_FE_INEXACT)
 
 check_include_file(mach/mach.h HAVE_MACH_MACH_H)
-check_include_file(histedit.h HAVE_HISTEDIT_H)
 check_include_file(CrashReporterClient.h HAVE_CRASHREPORTERCLIENT_H)
 if(APPLE)
   include(CheckCSourceCompiles)
   CHECK_C_SOURCE_COMPILES("
      static const char *__crashreporter_info__ = 0;
      asm(\".desc ___crashreporter_info__, 0x10\");
      int main() { return 0; }"
     HAVE_CRASHREPORTER_INFO)

 endif()
 
 # Don't look for these libraries if we're using MSan, since uninstrumented third
 # party code may call MSan interceptors like strlen, leading to false positives.
 if(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
   # Don't look for these libraries on Windows.
   if (NOT PURE_WINDOWS)
     # Skip libedit if using ASan as it contains memory leaks.
-    if (LLVM_ENABLE_LIBEDIT AND HAVE_HISTEDIT_H AND NOT LLVM_USE_SANITIZER MATCHES ".*Address.*")
-      check_library_exists(edit el_init "" HAVE_LIBEDIT)
+    if (LLVM_ENABLE_LIBEDIT AND NOT LLVM_USE_SANITIZER MATCHES ".*Address.*")
+      # If histedit.h is in a non-standard path, find it in CMAKE_INCLUDE_PATH
+      find_file(HISTEDIT_FILE histedit.h)
+      get_filename_component(HISTEDIT_DIR "${HISTEDIT_FILE}" DIRECTORY CACHE)
+      check_include_file(histedit.h HAVE_HISTEDIT_H "-I${HISTEDIT_DIR}")
+
+      # If libedit.a is in a non-standard path, find it in CMAKE_LIBRARY_PATH
+      find_library(LIBEDIT_LIBRARY libedit.a)
+      get_filename_component(LIBEDIT_DIR "${LIBEDIT_LIBRARY}" DIRECTORY CACHE)
+      check_library_exists(edit el_init "${LIBEDIT_DIR}" HAVE_LIBEDIT)
     else()
+      set(HAVE_HISTEDIT_H 0)
       set(HAVE_LIBEDIT 0)
     endif()
     if(LLVM_ENABLE_TERMINFO)
       if(LLVM_ENABLE_TERMINFO STREQUAL FORCE_ON)
         find_package(Terminfo REQUIRED)
       else()
         find_package(Terminfo)
       endif()

llvm/lib/LineEditor/CMakeLists.txt

 if(HAVE_LIBEDIT)
-  set(link_libs edit)
+  set(link_libs ${LIBEDIT_LIBRARY})
+endif()
+if(HAVE_HISTEDIT_H)
+  include_directories(${HISTEDIT_DIR})
 endif()
 
 add_llvm_component_library(LLVMLineEditor
   LineEditor.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/LineEditor
 
   LINK_LIBS
   ${link_libs}
 
   LINK_COMPONENTS
   Support
   )