[clang] Add an option for hiding line numbers in diagnostics

[teemperor]

Summary

Clang offers a -f[no]-show-column flag for hiding the column numbers when printing diagnostics
but there is no option for doing the same with line numbers.

In LLDB having this option would be useful, as LLDB sometimes only knows the file name for a
SourceLocation and just assigns it the dummy line/column 1:1. These fake line/column numbers
are confusing to the user and LLDB should be able to tell clang to hide *both* the column and the
line number when rendering text diagnostics.

This patch adds a flag for also hiding the line numbers. It's not exposed via the command line flags
as it's most likely not very useful for any user and can lead to ambiguous output when the
user decides to only hide either the line or the column number (where file:1: ... could now refer
to both line 1 or column 1 depending on the compiler flags). LLDB can just access the DiagnosticOptions
directly when constructing its internal Clang instance.

The effect doesn't apply to Vi/MSVC style diagnostics because it's not defined how these diagnostic styles
would show an omitted line number (MSVC doesn't have such an option and Vi's line mode is theory
only supporting line numbers if I understand it correctly).

[thakis]

Generally seems fine, nits below:

clang/docs/UsersManual.rst

172

Can you say that this is enabled by default, and maybe make the example about fno- then? :)

clang/lib/Frontend/TextDiagnostic.cpp

832

put break on its own line, as-is the indentation is pretty misleading here :)

[teemperor]

• Fixed formatting in switch-case
• Fixed formatting in DiagnosticOptions.def

[teemperor]

clang/docs/UsersManual.rst

172

The text actually mentions the option is on by default (This option, which defaults to on, ) and there is an example for both enabled and disabled (the disabled one is in the last line). FWIW, this is actually just 1-1 copying the style of all the diagnostic options below, so if we want to make this more readable we probably should do the same for all other descriptions. I actually think that's a good idea as the default value is really hidden within the description.

I can make a followup review that fixes this for all the help text in the manual.

clang/lib/Frontend/TextDiagnostic.cpp

832

Thanks! seems I forgot to clang-format.

[thakis]

clang/test/Misc/diag-format.c

45

on 2nd thought: Hm, should we allow -fno-line -fshow-column? It makes the output ambiguous, and it doesn't seem very useful. Maybe fno-show-line should imply fno-show-column, and explicit fno-show-line fshow-column should produce an error?

[MaskRay]

Isn't DiagOpts->ShowLine sufficient? I don't think clang command line users will specify -fno-show-line...

[teemperor]

In D83038#2256974, @MaskRay wrote:

Isn't DiagOpts->ShowLine sufficient? I don't think clang command line users will specify -fno-show-line...

Yes, it's only a flag because that's how the other DiagOpts are tested. I don't think there is a lot of benefit for having the flag beside being consistent with the other options. If that simplifies things, I can also do test this with a unit test and remove all the command line changes?

[MaskRay]

In D83038#2257143, @teemperor wrote:

In D83038#2256974, @MaskRay wrote:

Isn't DiagOpts->ShowLine sufficient? I don't think clang command line users will specify -fno-show-line...

Yes, it's only a flag because that's how the other DiagOpts are tested. I don't think there is a lot of benefit for having the flag beside being consistent with the other options. If that simplifies things, I can also do test this with a unit test and remove all the command line changes?

Yeah, sounds good if that can simplify things.

[teemperor]

• Removed driver arg and now tested via a unit test.

[MaskRay]

clang/unittests/Frontend/TextDiagnosticTest.cpp

32 ↗

(On Diff #290292)

The argument comments should use a style (with a equal sign) which can be detected by https://clang.llvm.org/extra/clang-tidy/checks/bugprone-argument-comment.html

38 ↗

(On Diff #290292)

; -> .

[teemperor]

• Fix typo and argument comments (thanks MaskRay !)

[teemperor]

@MaskRay is this ready to land? (This is technically in the 'accepted' state so this review probably disappeared from everyone's review queue, hence my ping)

[MaskRay]

clang/unittests/Frontend/TextDiagnosticTest.cpp

51 ↗

(On Diff #290420)

The argument comments should use a style (with a equal sign) which can be detected by https://clang.llvm.org/extra/clang-tidy/checks/bugprone-argument-comment.html

[teemperor]

• Also fix the remaining argument comments.

clang/docs/UsersManual.rst

 
 Clang aims to produce beautiful diagnostics by default, particularly for
 new users that first come to Clang. However, different people have
 different preferences, and sometimes Clang is driven not by a human,
 but by a program that wants consistent and easily parsable output. For
 these cases, Clang provides a wide range of options to control the exact
 output format of the diagnostics that it generates.
 
+.. _opt_fshow-line:
+
+**-f[no-]show-line**
+   Print line number in diagnostic.
+
+   This option, which defaults to on, controls whether or not Clang
+   prints the line number of a diagnostic. For example, when this is
+   enabled, Clang will print something like:
+
+   ::
+
+         test.c:28: warning: extra tokens at end of #endif directive [-Wextra-tokens]
+         #endif bad
+                ^
+                //
+
+   When this is disabled, Clang will print "test.c: warning..." with
+   no line number.
+
 .. _opt_fshow-column:
 
 **-f[no-]show-column**
    Print column number in diagnostic.
 
    This option, which defaults to on, controls whether or not Clang
    prints the column number of a diagnostic. For example, when this is
    enabled, Clang will print something like:

clang/include/clang/Basic/DiagnosticOptions.def

 #  define SEMANTIC_ENUM_DIAGOPT(Name, Type, Bits, Default) \
      ENUM_DIAGOPT(Name, Type, Bits, Default)
 #endif
 
 SEMANTIC_DIAGOPT(IgnoreWarnings, 1, 0)   /// -w
 DIAGOPT(NoRewriteMacros, 1, 0)  /// -Wno-rewrite-macros
 DIAGOPT(Pedantic, 1, 0)         /// -pedantic
 DIAGOPT(PedanticErrors, 1, 0)   /// -pedantic-errors
+DIAGOPT(ShowLine, 1, 1)       /// Show column number on diagnostics.
 DIAGOPT(ShowColumn, 1, 1)       /// Show column number on diagnostics.
 DIAGOPT(ShowLocation, 1, 1)     /// Show source location information.
 DIAGOPT(ShowLevel, 1, 1)        /// Show diagnostic level.
 DIAGOPT(AbsolutePath, 1, 0)     /// Use absolute paths.
 DIAGOPT(ShowCarets, 1, 1)       /// Show carets in diagnostics.
 DIAGOPT(ShowFixits, 1, 1)       /// Show fixit information.
 DIAGOPT(ShowSourceRanges, 1, 0) /// Show source ranges in numeric form.
 DIAGOPT(ShowParseableFixits, 1, 0) /// Show machine parseable fix-its.

clang/include/clang/Driver/Options.td

def fno_char8__t : Flag<["-"], "fno-char8_t">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Disable C++ builtin type char8_t">;
 def fshort_wchar : Flag<["-"], "fshort-wchar">, Group<f_Group>,
   HelpText<"Force wchar_t to be a short unsigned int">;
 def fno_short_wchar : Flag<["-"], "fno-short-wchar">, Group<f_Group>,
   HelpText<"Force wchar_t to be an unsigned int">;
 def fshow_overloads_EQ : Joined<["-"], "fshow-overloads=">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Which overload candidates to show when overload resolution fails: "
            "best|all; defaults to all">, Values<"best,all">;
+defm show_line : OptOutFFlag<"show-line", "", "Do not include line number on diagnostics">;
 defm show_column : OptOutFFlag<"show-column", "", "Do not include column number on diagnostics">;
 def fshow_source_location : Flag<["-"], "fshow-source-location">, Group<f_Group>;
 def fspell_checking : Flag<["-"], "fspell-checking">, Group<f_Group>;
 def fspell_checking_limit_EQ : Joined<["-"], "fspell-checking-limit=">, Group<f_Group>;
 def fsigned_bitfields : Flag<["-"], "fsigned-bitfields">, Group<f_Group>;
 defm signed_char : OptOutFFlag<"signed-char", "char is signed", "char is unsigned">;
 def fsplit_stack : Flag<["-"], "fsplit-stack">, Group<f_Group>;
 def fstack_protector_all : Flag<["-"], "fstack-protector-all">, Group<f_Group>,

clang/lib/Driver/ToolChains/Clang.cpp

static void RenderDiagnosticsOptions(const Driver &D, const ArgList &Args,
 
   if (!Args.hasFlag(options::OPT_fshow_source_location,
                     options::OPT_fno_show_source_location))
     CmdArgs.push_back("-fno-show-source-location");
 
   if (Args.hasArg(options::OPT_fdiagnostics_absolute_paths))
     CmdArgs.push_back("-fdiagnostics-absolute-paths");
 
+  if (!Args.hasFlag(options::OPT_fshow_line, options::OPT_fno_show_line))
+    CmdArgs.push_back("-fno-show-line");
+
   if (!Args.hasFlag(options::OPT_fshow_column, options::OPT_fno_show_column,
                     ColumnDefault))
     CmdArgs.push_back("-fno-show-column");
 
   if (!Args.hasFlag(options::OPT_fspell_checking,
                     options::OPT_fno_spell_checking))
     CmdArgs.push_back("-fno-spell-checking");
 }

clang/lib/Frontend/CompilerInvocation.cpp

if (Arg *A =
           Args.getLastArg(OPT_diagnostic_serialized_file, OPT__serialize_diags))
     Opts.DiagnosticSerializationFile = A->getValue();
   Opts.IgnoreWarnings = Args.hasArg(OPT_w);
   Opts.NoRewriteMacros = Args.hasArg(OPT_Wno_rewrite_macros);
   Opts.Pedantic = Args.hasArg(OPT_pedantic);
   Opts.PedanticErrors = Args.hasArg(OPT_pedantic_errors);
   Opts.ShowCarets = !Args.hasArg(OPT_fno_caret_diagnostics);
   Opts.ShowColors = parseShowColorsArgs(Args, DefaultDiagColor);
+  Opts.ShowLine = !Args.hasArg(OPT_fno_show_line);
   Opts.ShowColumn = !Args.hasArg(OPT_fno_show_column);
   Opts.ShowFixits = !Args.hasArg(OPT_fno_diagnostics_fixit_info);
   Opts.ShowLocation = !Args.hasArg(OPT_fno_show_source_location);
   Opts.AbsolutePath = Args.hasArg(OPT_fdiagnostics_absolute_paths);
   Opts.ShowOptionNames = !Args.hasArg(OPT_fno_diagnostics_show_option);
 
   llvm::sys::Process::UseANSIEscapeCodes(Args.hasArg(OPT_fansi_escape_codes));
 

clang/lib/Frontend/TextDiagnostic.cpp

void TextDiagnostic::emitDiagnosticLoc(FullSourceLoc Loc, PresumedLoc PLoc,
   if (!DiagOpts->ShowLocation)
     return;
 
   if (DiagOpts->ShowColors)
     OS.changeColor(savedColor, true);
 
   emitFilename(PLoc.getFilename(), Loc.getManager());
   switch (DiagOpts->getFormat()) {
-  case DiagnosticOptions::Clang: OS << ':'  << LineNo; break;
+  case DiagnosticOptions::Clang:
+      if (DiagOpts->ShowLine)
+        OS << ':'  << LineNo; break;
   case DiagnosticOptions::MSVC:  OS << '('  << LineNo; break;
   case DiagnosticOptions::Vi:    OS << " +" << LineNo; break;
   }
 
   if (DiagOpts->ShowColumn)
     // Compute the column number.
     if (unsigned ColNo = PLoc.getColumn()) {
       if (DiagOpts->getFormat() == DiagnosticOptions::MSVC) {

clang/test/Misc/diag-format.c

 // RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -target x86_64-pc-win32 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC
 // RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -fmsc-version=1900 -target x86_64-pc-win32 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2015
 // RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -fms-compatibility-version=13.00 -target x86_64-pc-win32 -fshow-column %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2010
 // RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -fmsc-version=1800 -target x86_64-pc-win32 -fshow-column %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2013
 // RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -target x86_64-pc-win32 -fshow-column %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC
 // RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -fmsc-version=1900 -target x86_64-pc-win32 -fshow-column %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2015
 //
 // RUN: %clang -fsyntax-only -fdiagnostics-format=vi    %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=VI
+// RUN: %clang -fsyntax-only -fdiagnostics-format=vi -fno-show-line   %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=VI
 //
 // RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -fno-show-column -fmsc-version=1900 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2015_ORIG
+// RUN: %clang -fsyntax-only -fdiagnostics-format=msvc -fno-show-column -fno-show-line -fmsc-version=1900 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2015_ORIG
 //
 // RUN: %clang -fsyntax-only -fno-show-column %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=NO_COLUMN
+// RUN: %clang -fsyntax-only -fno-show-line %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=NO_LINE
+// RUN: %clang -fsyntax-only -fno-show-column -fno-show-line %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=NO_LINE_NO_COLUMN
 //
 // RUN: not %clang -fsyntax-only -Werror -fdiagnostics-format=msvc-fallback -fmsc-version=1300 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2010-FALLBACK
 // RUN: not %clang -fsyntax-only -Werror -fdiagnostics-format=msvc-fallback -fms-compatibility-version=13.00 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2010-FALLBACK
 // RUN: not %clang -fsyntax-only -Werror -fdiagnostics-format=msvc-fallback -fmsc-version=1800 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2013-FALLBACK
 // RUN: not %clang -fsyntax-only -Werror -fdiagnostics-format=msvc-fallback -fmsc-version=1900 %s 2>&1 | FileCheck %s --strict-whitespace -check-prefix=MSVC2015-FALLBACK
 
 
 
-
-
-
-
 #ifdef foo
 #endif bad // extension!
 // DEFAULT: {{.*}}:36:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // MSVC2010: {{.*}}(36,7) : warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // MSVC2013: {{.*}}(36,8) : warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // MSVC: {{.*\(36,[78]\) ?}}: warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // MSVC2015: {{.*}}(36,8): warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // VI: {{.*}} +36:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // MSVC2015_ORIG: {{.*}}(36): warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // NO_COLUMN: {{.*}}:36: warning: extra tokens at end of #endif directive [-Wextra-tokens]
+// NO_LINE: {{.*}}format.c:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
+// NO_LINE_NO_COLUMN: {{.*}}format.c: warning: extra tokens at end of #endif directive [-Wextra-tokens]
 // MSVC2010-FALLBACK: {{.*}}(36,7) : error(clang): extra tokens at end of #endif directive
 // MSVC2013-FALLBACK: {{.*}}(36,8) : error(clang): extra tokens at end of #endif directive
 // MSVC2015-FALLBACK: {{.*}}(36,8): error(clang): extra tokens at end of #endif directive
 int x;