aaron.ballman added inline comments.
================
Comment at: clang/docs/LanguageExtensions.rst:3968-3984
+Final Macros
+============
+
+Clang supports the pragma ``#pragma clang final``, which can be used to
+mark macros as final, meaning they cannot be undef'd or re-defined. For
example:
+
+.. code-block:: c
----------------
Design question: would it make sense to extend this slightly so that the macro
does not have to be defined in order to be finalized? e.g., this could be used
as a way for a library author to say "this identifier cannot be defined as a
macro"?
================
Comment at: clang/docs/LanguageExtensions.rst:3979
+ #undef FINAL_MACRO // warning: FINAL_MACRO is marked final and should not
be undefined
+ #define FINAL_MACRO // warning: FINAL_MACRO is marked final and should not
be redefined
+
----------------
What happens if the redefinition is to the same token sequence as the original
definition? e.g.,
```
#define FINAL_MACRO 1+1
#pragma clang final(FINAL_MACRO)
#define FINAL_MACRO 1+1 // ok?
#define FINAL_MACRO (1+1) // Whoa...slow your roll there, champ!
```
================
Comment at: clang/include/clang/Basic/DiagnosticLexKinds.td:544
+ ExtWarn<"macro %0 has been marked as final and should not be "
+ "%select{un|re}1defined">,
+ InGroup<FinalMacro>;
----------------
Heh, I like your approach, but a goal of %select is to ease translation of our
diagnostics to other languages (in theory, anyway).
================
Comment at: clang/include/clang/Basic/IdentifierTable.h:196
+ // If this is a final macro, make the deprecation and header unsafe bits
+ // stick around after the undefinition so they apply to any redefinitions
+ if (!IsFinal) {
----------------
================
Comment at: clang/include/clang/Lex/Preprocessor.h:828
- /// Usage warning for macros marked by #pragma clang restrict_expansion.
- llvm::DenseMap<const IdentifierInfo *, MsgLocationPair>
- RestrictExpansionMacroMsgs;
+ /// Warning information for macro annotations
+ llvm::DenseMap<const IdentifierInfo *, MacroAnnotations> AnnotationInfos;
----------------
================
Comment at: clang/lib/Lex/Pragma.cpp:2083
+ if (!II->hasMacroDefinition()) {
+ PP.Diag(Tok, diag::err_pp_visibility_non_macro) << II->getName();
+ return;
----------------
This should cause the macro name to be properly quoted in the diagnostic.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D108567/new/
https://reviews.llvm.org/D108567
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