[Diagnostics] Don't drop a statically set NoWarningAsError flag during option processing

[wolfgangp]

Summary

Fixes PR 51837.

When a -W<diag> option is given on the command line, and the corresponding diangostic has the NoWarnOnError flag set, the flag is dropped when the severity is reevaluated, possibly as a result of a pragma or of command line processing.

[wolfgangp]

ping ...

[wolfgangp]

ping ...

[wolfgangp]

ping ...

[dexonsmith]

LGTM.

clang/test/Lexer/pragma-message.c

14

Might be nice to delete a blank line above to avoid triggering all these line number changes. (That said, I don't really understand why they're listed at all, given that -verify handles line numbers... maybe we want to be sure the macros work in this context?)

clang/lib/Basic/Diagnostic.cpp

if (Info.getSeverity() == diag::Severity::Error ||
         Info.getSeverity() == diag::Severity::Fatal) {
       Map = Info.getSeverity();
       WasUpgradedFromWarning = true;
     }
   }
   DiagnosticMapping Mapping = makeUserMapping(Map, L);
   Mapping.setUpgradedFromWarning(WasUpgradedFromWarning);
 
+  // Make sure we propagate the NoWarningAsError flag from an existing
+  // mapping (which may be the default mapping).
+  DiagnosticMapping &Info = GetCurDiagState()->getOrAddMapping(Diag);
+  Mapping.setNoWarningAsError(Info.hasNoWarningAsError() ||
+                              Mapping.hasNoWarningAsError());
+
   // Common case; setting all the diagnostics of a group in one place.
   if ((L.isInvalid() || L == DiagStatesByLoc.getCurDiagStateLoc()) &&
       DiagStatesByLoc.getCurDiagState()) {
     // FIXME: This is theoretically wrong: if the current state is shared with
     // some other location (via push/pop) we will change the state for that
     // other location as well. This cannot currently happen, as we can't update
     // the diagnostic state at the same location at which we pop.
     DiagStatesByLoc.getCurDiagState()->setMapping(Diag, Mapping);

clang/test/Lexer/pragma-message.c

 /* Test pragma message directive from
    http://msdn.microsoft.com/en-us/library/x7dkzch2.aspx */
-
 // message: Sends a string literal to the standard output without terminating
 // the compilation.
 // #pragma message(messagestring)
 // OR
 // #pragma message messagestring
 //
 // RUN: %clang_cc1 -fsyntax-only -verify -Werror %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Werror -W#pragma-messages %s
 #define STRING2(x) #x
 #define STRING(x) STRING2(x)
 #pragma message(":O I'm a message! " STRING(__LINE__)) // expected-warning {{:O I'm a message! 13}}
 #pragma message ":O gcc accepts this! " STRING(__LINE__) // expected-warning {{:O gcc accepts this! 14}}
 
 #pragma message(invalid) // expected-error {{expected string literal in pragma message}}
 
 // GCC supports a similar pragma, #pragma GCC warning (which generates a warning
 // message) and #pragma GCC error (which generates an error message).
 
 #pragma GCC warning(":O I'm a message! " STRING(__LINE__)) // expected-warning {{:O I'm a message! 21}}
 #pragma GCC warning ":O gcc accepts this! " STRING(__LINE__) // expected-warning {{:O gcc accepts this! 22}}