[libc] change ASAN condition to generator expression

[michaelrj]

Summary

Previously, building LLVM-libc with GWP ASAN was conditioned on the flag
COMPILER_RT_BUILD_GWP_ASAN, which caused issues do to the default value
of the flag being set in the compiler-rt cmake, which is seperate. Now
GWP ASAN is included based on if it exists as a target, which is more
consistent.

[sivachandra]

libc/src/stdlib/CMakeLists.txt

216

Using it in an if block does not seem to change the semantics. However, the following works for me:

list(APPEND SCUDO_DEPS $<$<TARGET_EXISTS:RTGwpAsan.${LIBC_TARGET_ARCHITECTURE}>:RTGwpAsan.${LIBC_TARGET_ARCHITECTURE}>
                       $<$<TARGET_EXISTS:RTGwpAsanBacktraceLibc.${LIBC_TARGET_ARCHITECTURE}>:RTGwpAsanBacktraceLibc.${LIBC_TARGET_ARCHITECTURE}>
                       $<$<TARGET_EXISTS:RTGwpAsanSegvHandler.${LIBC_TARGET_ARCHITECTURE}>:RTGwpAsanSegvHandler.${LIBC_TARGET_ARCHITECTURE}>)

[michaelrj]

switch to TARGET_NAME_IF_EXISTS

[michaelrj]

move the checking to inside the library rules

libc/cmake/modules/LLVMLibCLibraryRules.cmake

if(NOT ((${dep_type} STREQUAL ${ENTRYPOINT_OBJ_TARGET_TYPE}) OR (${dep_type} STREQUAL ${ENTRYPOINT_EXT_TARGET_TYPE})))
                           "not an 'add_entrypoint_object' or 'add_entrypoint_external' target.")
     endif()
     collect_object_file_deps(${dep} recursive_deps)
     list(APPEND all_deps ${recursive_deps})
   endforeach(dep)
   list(REMOVE_DUPLICATES all_deps)
   set(objects "")
   foreach(dep IN LISTS all_deps)
-    list(APPEND objects $<TARGET_OBJECTS:${dep}>)
+    list(APPEND objects $<$<STREQUAL:$<TARGET_NAME_IF_EXISTS:${dep}>,${dep}>:$<TARGET_OBJECTS:${dep}>>)
   endforeach(dep)
 
   add_library(
     ${target_name}
     STATIC
     ${objects}
   )
   set_target_properties(${target_name}  PROPERTIES ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})

libc/src/stdlib/CMakeLists.txt

 if(LLVM_LIBC_INCLUDE_SCUDO)
   set(SCUDO_DEPS "")
 
   include(${LIBC_SOURCE_DIR}/../compiler-rt/cmake/Modules/AllSupportedArchDefs.cmake)
   if(NOT (LIBC_TARGET_ARCHITECTURE IN_LIST ALL_SCUDO_STANDALONE_SUPPORTED_ARCH))
     message(FATAL_ERROR "Architecture ${LIBC_TARGET_ARCHITECTURE} is not supported by SCUDO. 
       Either disable LLVM_LIBC_INCLUDE_SCUDO or change your target architecture.")
   endif()
-  list(APPEND SCUDO_DEPS RTScudoStandalone.${LIBC_TARGET_ARCHITECTURE} 
-       RTScudoStandaloneCWrappers.${LIBC_TARGET_ARCHITECTURE})
-  if((LIBC_TARGET_ARCHITECTURE IN_LIST ALL_GWP_ASAN_SUPPORTED_ARCH) 
-      AND COMPILER_RT_BUILD_GWP_ASAN)
-    list(APPEND SCUDO_DEPS RTGwpAsan.${LIBC_TARGET_ARCHITECTURE} 
-                            RTGwpAsanBacktraceLibc.${LIBC_TARGET_ARCHITECTURE} 
-                            RTGwpAsanSegvHandler.${LIBC_TARGET_ARCHITECTURE})
-  elseif(COMPILER_RT_BUILD_GWP_ASAN)
-    message(WARNING "Architecture ${LIBC_TARGET_ARCHITECTURE} is not supported by GWP-ASan. Skipping.")
-  endif()
+
+  list(APPEND SCUDO_DEPS RTScudoStandalone.${LIBC_TARGET_ARCHITECTURE}
+
+  list(APPEND SCUDO_DEPS
+    RTGwpAsan.${LIBC_TARGET_ARCHITECTURE}
+    RTGwpAsanBacktraceLibc.${LIBC_TARGET_ARCHITECTURE}
+    RTGwpAsanSegvHandler.${LIBC_TARGET_ARCHITECTURE}
+    )
   
   add_entrypoint_external(
     malloc
     DEPENDS
       ${SCUDO_DEPS}
   )
   add_entrypoint_external(
     calloc
     DEPENDS