[clang-scan-deps] Improve argument parsing to find target object file path.

[saudi]

Summary

This patch adds support for the joined version of -o (e.g. -ofilename) command parameter when reading the clang arguments.

It also fixes a bug, as the first occurence of -o was used instead of the last one.

[Bigcheese]

lgtm.

clang/test/ClangScanDeps/Inputs/target-filename-cdb.json

+[
+{
+  "directory": "DIR",
+  "command": "clang -E DIR/target-filename_input.cpp",
+  "file": "DIR/target-filename_input.cpp"
+},
+{
+  "directory": "DIR",
+  "command": "clang -E DIR/target-filename_input.cpp -o a.o",
+  "file": "DIR/target-filename_input.cpp"
+},
+{
+  "directory": "DIR",
+  "command": "clang -E DIR/target-filename_input.cpp -ob.o",
+  "file": "DIR/target-filename_input.cpp"
+},
+{
+  "directory": "DIR",
+  "command": "clang -E DIR/target-filename_input.cpp -o first.o -o last.o",
+  "file": "DIR/target-filename_input.cpp"
+}
+]

clang/test/ClangScanDeps/target-filename.cpp

+// RUN: rm -rf %t.dir
+// RUN: rm -rf %t.cdb
+// RUN: mkdir -p %t.dir
+// RUN: cp %s %t.dir/target-filename_input.cpp
+// RUN: mkdir %t.dir/Inputs
+// RUN: cp %S/Inputs/header.h %t.dir/Inputs/header.h
+// RUN: sed -e "s|DIR|%/t.dir|g" %S/Inputs/target-filename-cdb.json > %t.cdb
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 1 | FileCheck %s
+
+// CHECK: target-filename_input.o:
+// CHECK-NEXT: target-filename_input.cpp
+
+// CHECK-NEXT: a.o:
+// CHECK-NEXT: target-filename_input.cpp
+
+// CHECK-NEXT: b.o:
+// CHECK-NEXT: target-filename_input.cpp
+
+// CHECK-NEXT: last.o:
+// CHECK-NEXT: target-filename_input.cpp

clang/tools/clang-scan-deps/ClangScanDeps.cpp

AdjustingCompilations->appendArgumentsAdjuster(
         bool HasMT = false;
         bool HasMQ = false;
         bool HasMD = false;
         bool HasResourceDir = false;
         // We need to find the last -o value.
         if (!Args.empty()) {
           std::size_t Idx = Args.size() - 1;
           for (auto It = Args.rbegin(); It != Args.rend(); ++It) {
-            if (It != Args.rbegin()) {
-              if (Args[Idx] == "-o")
+            StringRef Arg = Args[Idx];
+            if (LastO.empty()) {
+              if (Arg == "-o" && It != Args.rbegin())
                 LastO = Args[Idx + 1];
-              if (Args[Idx] == "-MT")
-                HasMT = true;
-              if (Args[Idx] == "-MQ")
-                HasMQ = true;
-              if (Args[Idx] == "-MD")
-                HasMD = true;
-              if (Args[Idx] == "-resource-dir")
-                HasResourceDir = true;
-            }
+              else if (Arg.startswith("-o"))
+                LastO = Arg.drop_front(2).str();
+            }
+            if (Arg == "-MT")
+            if (Arg == "-MQ")
+            if (Arg == "-MD")
+            if (Arg == "-resource-dir")
             --Idx;
           }
         }
         // If there's no -MT/-MQ Driver would add -MT with the value of the last
         // -o option.
         tooling::CommandLineArguments AdjustedArgs = Args;
         AdjustedArgs.push_back("-o");
         AdjustedArgs.push_back("/dev/null");