Define LLDB_DISABLE_CURSES as a fallback for missing curses(3) or panel(3)

[krytarowski]

Summary

This enables build on NetBSD-7.0. It would be nice to have a fall-back for
externally provided ncurses via pkgsrc, but it's left after the scheduled drop
of the autoconf/gmake build system. For not it's not worth the effort.

[labath]

I don't approve of automagic dependencies. With this patch it won't be possible to force curses usage. Even if you specify -DLLDB_DISABLE_CURSES=0, it will still build (sure, it will show a message about not being found, but who reads those...) even if it can't find the library, leading to surprises further down the line. I recommend doing one of the following:

• Leave things as they are. It is already possible to disable curses with the right switch
• Tweak the error message to inform the user of possible actions (but leave it a fatal error). E.g., "Curses library not found. Please install the library or reconfigure with LLDB_DISABLE_CURSES=0."
• set LLDB_DISABLE_CURSES=1 on netbsd only. (less magic, it only depends on the platform, not it's runtime properties, which can change randomly)

[krytarowski]

I resign from this change. I will just go for -DLLDB_DISABLE_CURSES from command line on NetBSD-7.0.

cmake/modules/LLDBConfig.cmake

 set(LLDB_PROJECT_ROOT ${CMAKE_CURRENT_SOURCE_DIR})
 set(LLDB_SOURCE_ROOT "${CMAKE_CURRENT_SOURCE_DIR}/source")
 set(LLDB_INCLUDE_ROOT "${CMAKE_CURRENT_SOURCE_DIR}/include")
 
+include(CheckIncludeFiles)
+
 set(LLDB_LINKER_SUPPORTS_GROUPS OFF)
 if (LLVM_COMPILER_IS_GCC_COMPATIBLE AND NOT "${CMAKE_SYSTEM_NAME}" MATCHES "Darwin")
   # The Darwin linker doesn't understand --start-group/--end-group.
   set(LLDB_LINKER_SUPPORTS_GROUPS ON)
 endif()
 
 if ( CMAKE_SYSTEM_NAME MATCHES "Windows" )
   set(LLDB_DEFAULT_DISABLE_PYTHON 0)
else()
   # cache variable.
   set(LLDB_EXPORT_ALL_SYMBOLS 0)
 endif()
 
 if ((NOT MSVC) OR MSVC12)
   add_definitions( -DHAVE_ROUND )
 endif()
 
+if (NOT LLDB_DISABLE_CURSES)
+    find_package(Curses)
+
+    find_library(CURSES_PANEL_LIBRARY NAMES panel DOC "The curses panel library")
+    check_include_files(panel.h HAVE_PANEL_H)
+    if (NOT CURSES_FOUND OR NOT CURSES_PANEL_LIBRARY OR NOT HAVE_PANEL_H)
+        message("-- Unable to find pair curses and libpanel")
+        set(LLDB_DISABLE_CURSES 1)
+    else ()
+        # Add panels to the library path
+        set (CURSES_LIBRARIES ${CURSES_LIBRARIES} ${CURSES_PANEL_LIBRARY})
+
+        list(APPEND system_libs ${CURSES_LIBRARIES})
+        include_directories(${CURSES_INCLUDE_DIR})
+    endif ()
+endif ()
+
 if (LLDB_DISABLE_CURSES)
   add_definitions( -DLLDB_DISABLE_CURSES )
 endif()
 
 # On Windows, we can't use the normal FindPythonLibs module that comes with CMake,
 # for a number of reasons.
 # 1) Prior to MSVC 2015, it is only possible to embed Python if python itself was
 #    compiled with an identical version (and build configuration) of MSVC as LLDB.

 
 # Figure out if lldb could use debugserver.  If so, then we'll
 # ensure we build debugserver when we build lldb.
 if ( CMAKE_SYSTEM_NAME MATCHES "Darwin" )
     set(LLDB_CAN_USE_DEBUGSERVER 1)
 else()
     set(LLDB_CAN_USE_DEBUGSERVER 0)
 endif()
-
-if (NOT LLDB_DISABLE_CURSES)
-    find_package(Curses REQUIRED)
-
-    find_library(CURSES_PANEL_LIBRARY NAMES panel DOC "The curses panel library")
-    if (NOT CURSES_PANEL_LIBRARY)
-        message(FATAL_ERROR "A required curses' panel library not found.")
-    endif ()
-
-    # Add panels to the library path
-    set (CURSES_LIBRARIES ${CURSES_LIBRARIES} ${CURSES_PANEL_LIBRARY})
-
-    list(APPEND system_libs ${CURSES_LIBRARIES})
-    include_directories(${CURSES_INCLUDE_DIR})
-endif ()