[PATCH] D55628: Add support for "labels" on push/pop directives in #pragma clang attribute

[Erik Pilkington via Phabricator via cfe-commits]

erik.pilkington created this revision.
erik.pilkington added reviewers: arphaman, aaron.ballman.
Herald added subscribers: dexonsmith, jkorous.

One problem with defining macros that expand to _Pragma("clang attribute")` is that they don't nest very well:

  // In some header...
  #define ASSUME_X_BEGIN _Pragma ("clang attribute push(__attribute__((x)), apply_to=variable)")
  #define ASSUME_X_END _Pragma ("clang attribute pop")
  
  #define ASSUME_Y_BEGIN _Pragma("clang attribute push(__attribute__((y)), apply_to=variable)")
  #define ASSUME_Y_END _Pragma("clang attribute pop")
  
  // in some source file...
  
  ASSUME_X_BEGIN
  // lots of code
  ASSUME_Y_BEGIN
  // some more code
  ASSUME_X_END // oops! Popped Y, but meant to pop X.
  // some other code
  ASSUME_Y_END // ditto

This patch adds a way to fix this by adding labels to push/pop directives. A `clang attribute pop`s with a label will only pop a `push`ed group with that same label. Macro authors can then add a unique label to their BEGIN/END functions, which would cause the code above to work fine.

Thanks for taking a look!
Erik


Repository:
  rC Clang

https://reviews.llvm.org/D55628

Files:
  clang/docs/LanguageExtensions.rst
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/include/clang/Sema/Sema.h
  clang/lib/Parse/ParsePragma.cpp
  clang/lib/Sema/SemaAttr.cpp
  clang/test/Sema/pragma-attribute-label.c

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