[Clang] Use -main-file-name for source filename if not set

[the_jk]

Summary

-main-file-name is currently used to set the source name used in debug information.

If the source filename is "-" and -main-file-name is set, then use the filename also for source_filename and ModuleID of the output.

The argument is generally used outside the internal clang calls when running clang in a wrapper like icecc which gives the source via stdin but still wants to get a object file with the original source filename both in debug info and IR code.

[the_jk]

Forgot to link: https://bugs.llvm.org/show_bug.cgi?id=43250

[tejohnson]

Please upload patches with context (https://llvm.org/docs/Phabricator.html#requesting-a-review-via-the-web-interface)

I'm not terribly familiar with this part of clang, but my concern would be that overriding the PresumedInputFile here could have unintended side effects. How about simply overriding the source file name on the Module object that eventually gets created, if it is "-"? I believe that is in the CodeGeneratorImpl constructor, and the CodeGenOptions are available there.

[the_jk]

Moved ModuleName change to CodeGeneratorImpl as suggested, agree that it seems to fit well there.

[tejohnson]

lgtm

[the_jk]

I don't have commit access so I'd need someone to push this, thanks.

[tejohnson]

In D67592#1686898, @the_jk wrote:

I don't have commit access so I'd need someone to push this, thanks.

I can commit for you today.

[the_jk]

Great, thanks again.

[thakis]

This is failing on my mac like so:

FAIL: Clang :: Frontend/stdin-input.c (1 of 1)
******************** TEST 'Clang :: Frontend/stdin-input.c' FAILED ********************
Script:
--
: 'RUN: at line 1';   cat /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c | /Users/thakis/src/llvm-project/out/gn/bin/clang -emit-llvm -g -S  -Xclang -main-file-name -Xclang test/foo.c -x c - -o - | /Users/thakis/src/llvm-project/out/gn/bin/FileCheck /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c
--
Exit Code: 1

Command Output (stderr):
--
+ : 'RUN: at line 1'
+ cat /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c
+ /Users/thakis/src/llvm-project/out/gn/bin/clang -emit-llvm -g -S -Xclang -main-file-name -Xclang test/foo.c -x c - -o -
+ /Users/thakis/src/llvm-project/out/gn/bin/FileCheck /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c
/Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c:5:11: error: CHECK: expected string not found in input
// CHECK: !1 = !DIFile(filename: "test/foo.c"
          ^
<stdin>:3:1: note: scanning from here
target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
^
<stdin>:24:1: note: possible intended match here
!6 = !DIFile(filename: "test/foo.c", directory: "/Users/thakis/src/llvm-project/out/gn/obj/clang/test/Frontend")
^

--

********************
Testing Time: 0.06s
********************
Failing Tests (1):
    Clang :: Frontend/stdin-input.c

If I manually run bin/llvm-lit clang/test/Frontend/stdin-input.c it fails, but if I run the command it claims to be running it passes.

If I replace the FileCheck on the run line with > tmp.txt I see what the failing FileCheck is seeing:

!0 = !{i32 2, !"SDK Version", [2 x i32] [i32 10, i32 14]}
!1 = !{i32 2, !"Dwarf Version", i32 4}
!2 = !{i32 2, !"Debug Info Version", i32 3}
!3 = !{i32 1, !"wchar_size", i32 4}
!4 = !{i32 7, !"PIC Level", i32 2}
!5 = distinct !DICompileUnit(language: DW_LANG_C99, file: !6, producer: "clang version 10.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !7, nameTableKind: None)
!6 = !DIFile(filename: "test/foo.c", directory: "/Users/thakis/src/llvm-project/out/gn/obj/clang/test/Frontend")

I'm guessing lit sets some env var that makes clang emit these additional values (?)

[tejohnson]

In D67592#1688413, @thakis wrote:

This is failing on my mac like so:

This should be fixed by r373237. I didn't get any email with buildbot failures, but someone mailed one to me manually. Not sure why it only fails sometimes.

FAIL: Clang :: Frontend/stdin-input.c (1 of 1)
******************** TEST 'Clang :: Frontend/stdin-input.c' FAILED ********************
Script:
--
: 'RUN: at line 1';   cat /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c | /Users/thakis/src/llvm-project/out/gn/bin/clang -emit-llvm -g -S  -Xclang -main-file-name -Xclang test/foo.c -x c - -o - | /Users/thakis/src/llvm-project/out/gn/bin/FileCheck /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c
--
Exit Code: 1

Command Output (stderr):
--
+ : 'RUN: at line 1'
+ cat /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c
+ /Users/thakis/src/llvm-project/out/gn/bin/clang -emit-llvm -g -S -Xclang -main-file-name -Xclang test/foo.c -x c - -o -
+ /Users/thakis/src/llvm-project/out/gn/bin/FileCheck /Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c
/Users/thakis/src/llvm-project/clang/test/Frontend/stdin-input.c:5:11: error: CHECK: expected string not found in input
// CHECK: !1 = !DIFile(filename: "test/foo.c"
          ^
<stdin>:3:1: note: scanning from here
target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
^
<stdin>:24:1: note: possible intended match here
!6 = !DIFile(filename: "test/foo.c", directory: "/Users/thakis/src/llvm-project/out/gn/obj/clang/test/Frontend")
^

--

********************
Testing Time: 0.06s
********************
Failing Tests (1):
    Clang :: Frontend/stdin-input.c

If I manually run bin/llvm-lit clang/test/Frontend/stdin-input.c it fails, but if I run the command it claims to be running it passes.

If I replace the FileCheck on the run line with > tmp.txt I see what the failing FileCheck is seeing:

!0 = !{i32 2, !"SDK Version", [2 x i32] [i32 10, i32 14]}
!1 = !{i32 2, !"Dwarf Version", i32 4}
!2 = !{i32 2, !"Debug Info Version", i32 3}
!3 = !{i32 1, !"wchar_size", i32 4}
!4 = !{i32 7, !"PIC Level", i32 2}
!5 = distinct !DICompileUnit(language: DW_LANG_C99, file: !6, producer: "clang version 10.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !7, nameTableKind: None)
!6 = !DIFile(filename: "test/foo.c", directory: "/Users/thakis/src/llvm-project/out/gn/obj/clang/test/Frontend")

I'm guessing lit sets some env var that makes clang emit these additional values (?)

[thakis]

Yup, test is happy now, thanks!

clang/include/clang/Driver/CC1Options.td

 def version : Flag<["-"], "version">,
   HelpText<"Print the compiler version">;
 def main_file_name : Separate<["-"], "main-file-name">,
-  HelpText<"Main file name to use for debug info">;
+  HelpText<"Main file name to use for debug info and source if missing">;
 def split_dwarf_output : Separate<["-"], "split-dwarf-output">,
   HelpText<"File name to use for split dwarf debug info output">;
 

clang/lib/Frontend/FrontendAction.cpp

     std::string PresumedInputFile = getCurrentFileOrBufferName();
     if (Input.isPreprocessed())
       ReadOriginalFileName(CI, PresumedInputFile);
+    else if (PresumedInputFile == "-" &&
+             !CI.getCodeGenOpts().MainFileName.empty()) {
+      PresumedInputFile = CI.getCodeGenOpts().MainFileName;
+    }
 
     std::unique_ptr<ASTConsumer> Consumer =
         CreateWrappedASTConsumer(CI, PresumedInputFile);

clang/test/Frontend/stdin-input

+// RUN: cat %s | %clang -emit-llvm -g -S \
+// RUN: -Xclang -main-file-name -Xclang test/foo.c -x c - -o - | FileCheck %s
+// CHECK: ; ModuleID = 'test/foo.c'
+// CHECK: source_filename = "test/foo.c"
+// CHECK: !1 = !DIFile(filename: "test/foo.c"
+
+int main() {}
 No newline at end of file