Remove dependency on scan-build wrapper script for Clang analysis builds.

build/toolchain/gcc_toolchain.gni

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/clang/clang.gni")
 import("//build/config/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/v8_target_cpu.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/clang_static_analyzer.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 
+# Path to the Clang static analysis wrapper script.
+# REVIEWERS: can you suggest a better location for this?
+# GN is really picky about dead stores of variables except at the global scope.

[Nico, 2017/03/10 01:55:02]

I think the usual workaround is to assert() on the dead variable to suppress
that warning. Example:
https://cs.chromium.org/chromium/src/BUILD.gn?type=cs&q=assert+file:%5C.gn+pa...

+analyzer_wrapper =
+    rebase_path("//build/toolchain/clang_static_analyzer_wrapper.py",
+                root_build_dir)
+
 # This template defines a toolchain for something that works like gcc
 # (including clang).
 #
 # It requires the following variables specifying the executables to run:
 #  - ar
 #  - cc
 #  - cxx
 #  - ld
 #
 # Optional parameters that control the tools:
@@ skipping 94 matching lines @@
     if (defined(toolchain_args.use_goma)) {
       toolchain_uses_goma = toolchain_args.use_goma
     } else {
       toolchain_uses_goma = use_goma
     }
     if (defined(toolchain_args.cc_wrapper)) {
       toolchain_cc_wrapper = toolchain_args.cc_wrapper
     } else {
       toolchain_cc_wrapper = cc_wrapper
     }
+    assert(!(toolchain_cc_wrapper != "" && toolchain_uses_goma),
+           "Goma and cc_wrapper can't be used together.")
 
-    # Compute the compiler prefix.
+    # When the invoker has explicitly overridden use_goma or cc_wrapper in the
+    # toolchain args, use those values, otherwise default to the global one.
+    # This works because the only reasonable override that toolchains might
+    # supply for these values are to force-disable them.
     if (toolchain_uses_goma) {
-      assert(toolchain_cc_wrapper == "",
-             "Goma and cc_wrapper can't be used together.")
-      compiler_prefix = "$goma_dir/gomacc "
-    } else if (toolchain_cc_wrapper != "") {
-      compiler_prefix = toolchain_cc_wrapper + " "
+      goma_path = "$goma_dir/gomacc"
+
+      # Use the static analysis script if static analysis is turned on
+      # AND the tool has not opted out by setting
+      # 'is_clang_static_analysis_supported' to false.
+      if (is_clang && use_clang_static_analyzer &&
+          (!defined(invoker.is_clang_analysis_supported) ||
+           invoker.is_clang_analysis_supported)) {
+        compiler_prefix = "${analyzer_wrapper} ${goma_path} "
+
+        # Create a distinct variable for "asm", since analysis runs pass
+        # a bunch of flags to clang/clang++ that are nonsensical on assembler
+        # runs.
+        asm = "${goma_path} ${invoker.cc}"
+      } else {
+        compiler_prefix = "${goma_path} "
+      }
     } else {
-      compiler_prefix = ""
+      if (is_clang && use_clang_static_analyzer &&
+          (!defined(invoker.is_clang_analysis_supported) ||
+           invoker.is_clang_analysis_supported)) {
+        compiler_prefix = "${analyzer_wrapper} "
+        asm = invoker.cc
+      } else {
+        compiler_prefix = "${toolchain_cc_wrapper} "
+      }
     }
 
     cc = compiler_prefix + invoker.cc
     cxx = compiler_prefix + invoker.cxx
     ar = invoker.ar
     ld = invoker.ld
+    if (!defined(asm)) {
+      asm = cc
+    }
     if (defined(invoker.readelf)) {
       readelf = invoker.readelf
     } else {
       readelf = "readelf"
     }
     if (defined(invoker.nm)) {
       nm = invoker.nm
     } else {
       nm = "nm"
     }
@@ skipping 98 matching lines @@
         compile_wrapper =
             rebase_path("//build/toolchain/gcc_compile_wrapper.py",
                         root_build_dir)
         command = "$python_path \"$compile_wrapper\" --resource-whitelist=\"{{output}}.whitelist\" $command"
       }
     }
 
     tool("asm") {
       # For GCC we can just use the C compiler to compile assembly.
       depfile = "{{output}}.d"
-      command = "$cc -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{asmflags}} -c {{source}} -o {{output}}"
+      command = "$asm -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{asmflags}} -c {{source}} -o {{output}}"
       depsformat = "gcc"
       description = "ASM {{output}}"
       outputs = [
         "$object_subdir/{{source_name_part}}.o",
       ]
     }
 
     tool("alink") {
       rspfile = "{{output}}.rsp"
       whitelist_flag = " "
@@ skipping 206 matching lines @@
     toolprefix = invoker.toolprefix
   } else {
     toolprefix = ""
   }
 
   gcc_toolchain(target_name) {
     prefix = rebase_path("$clang_base_path/bin", root_build_dir)
     cc = "$prefix/clang"
     cxx = "$prefix/clang++"
     ld = cxx
-
-    if (use_clang_static_analyzer) {
-      # Static analysis isn't supported under GOMA. See crbug.com/687245
-      # for progress on this issue.
-      assert(!use_goma, "'use_clang_static_analyzer' cannot be used with GOMA.")
-
-      # Call "ccc-analyzer" or "c++-analyzer" instead of directly calling Clang.
-      # |wrapper_tool| sets the environment variables which are read by the
-      # analyzer tools.
-      analyzer_wrapper =
-          rebase_path("//build/toolchain/clang_static_analyzer_wrapper.py",
-                      root_build_dir)
-      cc = analyzer_wrapper + " --clang-cc-path=${cc} --analyzer=" +
-           rebase_path("//third_party/scan-build/src/libexec/ccc-analyzer",
-                       root_build_dir)
-      cxx = analyzer_wrapper + " --clang-cxx-path=${cxx} --analyzer=" +
-            rebase_path("//third_party/scan-build/src/libexec/c++-analyzer",
-                        root_build_dir)
-    }
-
     readelf = "${toolprefix}readelf"
     ar = "${toolprefix}ar"
     nm = "${toolprefix}nm"
 
-    forward_variables_from(invoker, [ "strip" ])
+    forward_variables_from(invoker,
+                           [
+                             "strip",
+                             "is_clang_analysis_supported",
+                           ])
 
     toolchain_args = {
       if (defined(invoker.toolchain_args)) {
         forward_variables_from(invoker.toolchain_args, "*")
       }
       is_clang = true
     }
   }
 }