[clang] Fix assertion failure using -MJ with -fsyntax-only

[benlangmuir]

Summary

If there is no output filename we should not assert when writing output for -MJ.

[MaskRay]

Looks great!

clang/test/Driver/compilation_database_fsyntax_only.c

1

The test can be added into compilation_database.c.

[benlangmuir]

clang/test/Driver/compilation_database_fsyntax_only.c

1

Done, thanks!

clang/lib/Driver/ToolChains/Clang.cpp

if (!CompilationDatabase) {
     CompilationDatabase = std::move(File);
   }
   auto &CDB = *CompilationDatabase;
   auto CWD = D.getVFS().getCurrentWorkingDirectory();
   if (!CWD)
     CWD = ".";
   CDB << "{ \"directory\": \"" << escape(*CWD) << "\"";
   CDB << ", \"file\": \"" << escape(Input.getFilename()) << "\"";
+  if (Output.isFilename())
     CDB << ", \"output\": \"" << escape(Output.getFilename()) << "\"";
   CDB << ", \"arguments\": [\"" << escape(D.ClangExecutable) << "\"";
   SmallString<128> Buf;
   Buf = "-x";
   Buf += types::getTypeName(Input.getType());
   CDB << ", \"" << escape(Buf) << "\"";
   if (!D.SysRoot.empty() && !Args.hasArg(options::OPT__sysroot_EQ)) {
     Buf = "--sysroot=";
     Buf += D.SysRoot;
     CDB << ", \"" << escape(Buf) << "\"";
   }
   CDB << ", \"" << escape(Input.getFilename()) << "\"";
+  if (Output.isFilename())
     CDB << ", \"-o\", \"" << escape(Output.getFilename()) << "\"";
   for (auto &A: Args) {
     auto &O = A->getOption();
     // Skip language selection, which is positional.
     if (O.getID() == options::OPT_x)
       continue;
     // Skip writing dependency output and the compilation database itself.
     if (O.getGroup().isValid() && O.getGroup().getID() == options::OPT_M_Group)
       continue;

clang/test/Driver/compilation_database_fsyntax_only.c

+// RUN: mkdir -p %t.workdir && cd %t.workdir
+// RUN: %clang -fsyntax-only %s -MJ - 2>&1 | FileCheck %s
+
+// CHECK:      {
+// CHECK-SAME: "directory": "{{[^"]*}}workdir",
+// CHECK-SAME: "file": "{{[^"]*}}compilation_database_fsyntax_only.c"
+// CHECK-NOT:  "output"
+// CHECK-SAME: "arguments": [
+// CHECK-NOT:    "-o"
+// CHECK-SAME: ]
+// CHECK-SAME: }
+
+
+int main(void) {
+  return 0;
+}