[libFuzzer] Always build libFuzzer

There are two reasons why users might want to build libfuzzer:
- To fuzz LLVM itself
- To get the libFuzzer.a archive file, so that they can attach it to their code
This change always builds libfuzzer, and supports the second use case if the specified flag is set.

The point of this patch is to have something that can potentially be shipped with the compiler, and this also ensures that the version of libFuzzer is correct to use with that compiler.

Patch by George Karpenkov.

Differential Revision: https://reviews.llvm.org/D32096

llvm-svn: 301054

llvm/lib/Fuzzer/CMakeLists.txt

@@ -13,51 +13,57 @@ if( APPLE )
   endif()
 endif()
 
-set(LIBFUZZER_FLAGS_BASE "${CMAKE_CXX_FLAGS}")
-# Disable the coverage and sanitizer instrumentation for the fuzzer itself.
-set(CMAKE_CXX_FLAGS "${LIBFUZZER_FLAGS_BASE} -fno-sanitize-coverage=trace-pc-guard,edge,trace-cmp,indirect-calls,8bit-counters -Werror")
 if( LLVM_USE_SANITIZE_COVERAGE )
   if(NOT "${LLVM_USE_SANITIZER}" STREQUAL "Address")
     message(FATAL_ERROR
       "LibFuzzer and its tests require LLVM_USE_SANITIZER=Address and "
       "LLVM_USE_SANITIZE_COVERAGE=YES to be set."
       )
   endif()
+  set(LIBFUZZER_FLAGS_BASE "${CMAKE_CXX_FLAGS}")
+
+  # Disable the coverage and sanitizer instrumentation for the fuzzer itself.
+  set(CMAKE_CXX_FLAGS "${LIBFUZZER_FLAGS_BASE} -fno-sanitize-coverage=trace-pc-guard,edge,trace-cmp,indirect-calls,8bit-counters -Werror")
+endif()
+
+# Compile libFuzzer if the compilation is specifically requested, OR
+# if the platform is known to be working.
+if ( LLVM_USE_SANITIZE_COVERAGE OR CMAKE_SYSTEM_NAME MATCHES "Darwin|Linux" )
   add_library(LLVMFuzzerNoMainObjects OBJECT
-    FuzzerCrossOver.cpp
-    FuzzerDriver.cpp
-    FuzzerExtFunctionsDlsym.cpp
-    FuzzerExtFunctionsDlsymWin.cpp
-    FuzzerExtFunctionsWeak.cpp
-    FuzzerExtraCounters.cpp
-    FuzzerIO.cpp
-    FuzzerIOPosix.cpp
-    FuzzerIOWindows.cpp
-    FuzzerLoop.cpp
-    FuzzerMerge.cpp
-    FuzzerMutate.cpp
-    FuzzerSHA1.cpp
-    FuzzerShmemPosix.cpp
-    FuzzerShmemWindows.cpp
-    FuzzerTracePC.cpp
-    FuzzerTraceState.cpp
-    FuzzerUtil.cpp
-    FuzzerUtilDarwin.cpp
-    FuzzerUtilLinux.cpp
-    FuzzerUtilPosix.cpp
-    FuzzerUtilWindows.cpp
-    )
+      FuzzerCrossOver.cpp
+      FuzzerDriver.cpp
+      FuzzerExtFunctionsDlsym.cpp
+      FuzzerExtFunctionsDlsymWin.cpp
+      FuzzerExtFunctionsWeak.cpp
+      FuzzerExtraCounters.cpp
+      FuzzerIO.cpp
+      FuzzerIOPosix.cpp
+      FuzzerIOWindows.cpp
+      FuzzerLoop.cpp
+      FuzzerMerge.cpp
+      FuzzerMutate.cpp
+      FuzzerSHA1.cpp
+      FuzzerShmemPosix.cpp
+      FuzzerShmemWindows.cpp
+      FuzzerTracePC.cpp
+      FuzzerTraceState.cpp
+      FuzzerUtil.cpp
+      FuzzerUtilDarwin.cpp
+      FuzzerUtilLinux.cpp
+      FuzzerUtilPosix.cpp
+      FuzzerUtilWindows.cpp
+      )
   add_library(LLVMFuzzerNoMain STATIC
-    $<TARGET_OBJECTS:LLVMFuzzerNoMainObjects>
-    )
+      $<TARGET_OBJECTS:LLVMFuzzerNoMainObjects>
+      )
   target_link_libraries(LLVMFuzzerNoMain ${LLVM_PTHREAD_LIB})
   add_library(LLVMFuzzer STATIC
-    FuzzerMain.cpp
-    $<TARGET_OBJECTS:LLVMFuzzerNoMainObjects>
-    )
+      FuzzerMain.cpp
+      $<TARGET_OBJECTS:LLVMFuzzerNoMainObjects>
+      )
   target_link_libraries(LLVMFuzzer ${LLVM_PTHREAD_LIB})
+endif()
 
-  if( LLVM_INCLUDE_TESTS )
-    add_subdirectory(test)
-  endif()
+if( LLVM_USE_SANITIZE_COVERAGE AND LLVM_INCLUDE_TESTS )
+  add_subdirectory(test)
 endif()