dnrops
/
clang
mirror of https://github.com/microsoft/clang.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Improved support for removing the comma preceding __VA_ARGS__ where __VA_ARGS__ 

is empty in a variadic macro expansion.  This fixes a divergence in support for
the ", ## __VA_ARGS__" GCC extension which differed in behaviour when in strict
C99 mode (note: there is no change in behaviour has been made in the gnu99 mode
that clang uses by default).  In addition, there is improved support for the
Microsoft alternative extension ", __VA_ARGS__".

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167613 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andy Gibbs 2012-11-09 13:24:30 +00:00
parent 1a52a4d36c
commit 02f0022dfc
2 changed files with 128 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

81
lib/Lex/TokenLexer.cpp
View File

@ -119,6 +119,55 @@ void TokenLexer::destroy() {
if (ActualArgs) ActualArgs->destroy(PP);
}
/// Remove comma ahead of __VA_ARGS__, if present, according to compiler dialect
/// settings. Returns true if the comma is removed.
static bool MaybeRemoveCommaBeforeVaArgs(SmallVector<Token, 128> &ResultToks,
bool &NextTokGetsSpace,
bool HasPasteOperator,
MacroInfo *Macro, unsigned MacroArgNo,
Preprocessor &PP) {
// Is the macro argument __VA_ARGS__?
if (!Macro->isVariadic() || MacroArgNo != Macro->getNumArgs()-1)
return false;
// In Microsoft-compatibility mode, a comma is removed in the expansion
// of " ... , __VA_ARGS__ " if __VA_ARGS__ is empty. This extension is
// not supported by gcc.
if (!HasPasteOperator && !PP.getLangOpts().MicrosoftMode)
return false;
// GCC removes the comma in the expansion of " ... , ## __VA_ARGS__ " if
// __VA_ARGS__ is empty, but not in strict C99 mode where there are no
// named arguments, where it remains. In all other modes, including C99
// with GNU extensions, it is removed regardless of named arguments.
// Microsoft also appears to support this extension, unofficially.
if (PP.getLangOpts().C99 && !PP.getLangOpts().GNUMode
&& Macro->getNumArgs() < 2)
return false;
// Is a comma available to be removed?
if (ResultToks.empty() || !ResultToks.back().is(tok::comma))
return false;
// Issue an extension diagnostic for the paste operator.
if (HasPasteOperator)
PP.Diag(ResultToks.back().getLocation(), diag::ext_paste_comma);
// Remove the comma.
ResultToks.pop_back();
// If the comma was right after another paste (e.g. "X##,##__VA_ARGS__"),
// then removal of the comma should produce a placemarker token (in C99
// terms) which we model by popping off the previous ##, giving us a plain
// "X" when __VA_ARGS__ is empty.
if (!ResultToks.empty() && ResultToks.back().is(tok::hashhash))
ResultToks.pop_back();
// Never add a space, even if the comma, ##, or arg had a space.
NextTokGetsSpace = false;
return true;
}
/// Expand the arguments of a function-like macro so that we can quickly
/// return preexpanded tokens from Tokens.
void TokenLexer::ExpandFunctionArguments() {
@ -199,6 +248,14 @@ void TokenLexer::ExpandFunctionArguments() {
!ResultToks.empty() && ResultToks.back().is(tok::hashhash);
bool PasteAfter = i+1 != e && Tokens[i+1].is(tok::hashhash);
// In Microsoft mode, remove the comma before __VA_ARGS__ to ensure there
// are no trailing commas if __VA_ARGS__ is empty.
if (!PasteBefore && ActualArgs->isVarargsElidedUse() &&
MaybeRemoveCommaBeforeVaArgs(ResultToks, NextTokGetsSpace,
/*HasPasteOperator=*/false,
Macro, ArgNo, PP))
continue;
// If it is not the LHS/RHS of a ## operator, we must pre-expand the
// argument and substitute the expanded tokens into the result. This is
// C99 6.10.3.1p1.
@ -321,23 +378,13 @@ void TokenLexer::ExpandFunctionArguments() {
// If this is the __VA_ARGS__ token, and if the argument wasn't provided,
// and if the macro had at least one real argument, and if the token before
// the ## was a comma, remove the comma.
if ((unsigned)ArgNo == Macro->getNumArgs()-1 && // is __VA_ARGS__
ActualArgs->isVarargsElidedUse() && // Argument elided.
!ResultToks.empty() && ResultToks.back().is(tok::comma)) {
// Never add a space, even if the comma, ##, or arg had a space.
NextTokGetsSpace = false;
// Remove the paste operator, report use of the extension.
PP.Diag(ResultToks.back().getLocation(), diag::ext_paste_comma);
ResultToks.pop_back();
// If the comma was right after another paste (e.g. "X##,##__VA_ARGS__"),
// then removal of the comma should produce a placemarker token (in C99
// terms) which we model by popping off the previous ##, giving us a plain
// "X" when __VA_ARGS__ is empty.
if (!ResultToks.empty() && ResultToks.back().is(tok::hashhash))
ResultToks.pop_back();
}
// the ## was a comma, remove the comma. This is a GCC extension which is
// disabled when using -std=c99.
if (ActualArgs->isVarargsElidedUse())
MaybeRemoveCommaBeforeVaArgs(ResultToks, NextTokGetsSpace,
/*HasPasteOperator=*/true,
Macro, ArgNo, PP);
continue;
}

64
test/Preprocessor/macro_fn_comma_swallow2.c Normal file
View File

@ -0,0 +1,64 @@
// Test the __VA_ARGS__ comma swallowing extensions of various compiler dialects.
// RUN: %clang_cc1 -E %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -std=c99 %s | FileCheck -check-prefix=C99 -strict-whitespace %s
// RUN: %clang_cc1 -E -std=c11 %s | FileCheck -check-prefix=C99 -strict-whitespace %s
// RUN: %clang_cc1 -E -x c++ %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -std=gnu99 %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -fms-compatibility %s | FileCheck -check-prefix=MS -strict-whitespace %s
// RUN: %clang_cc1 -E -DNAMED %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -std=c99 -DNAMED %s | FileCheck -check-prefix=C99 -strict-whitespace %s
#ifndef NAMED
# define A(...) [ __VA_ARGS__ ]
# define B(...) [ , __VA_ARGS__ ]
# define C(...) [ , ## __VA_ARGS__ ]
# define D(A,...) [ A , ## __VA_ARGS__ ]
# define E(A,...) [ __VA_ARGS__ ## A ]
#else
// These are the GCC named argument versions of the C99-style variadic macros.
// Note that __VA_ARGS__ *may* be used as the name, this is not prohibited!
# define A(__VA_ARGS__...) [ __VA_ARGS__ ]
# define B(__VA_ARGS__...) [ , __VA_ARGS__ ]
# define C(__VA_ARGS__...) [ , ## __VA_ARGS__ ]
# define D(A,__VA_ARGS__...) [ A , ## __VA_ARGS__ ]
# define E(A,__VA_ARGS__...) [ __VA_ARGS__ ## A ]
#endif
1: A() B() C() D() E()
2: A(a) B(a) C(a) D(a) E(a)
3: A(,) B(,) C(,) D(,) E(,)
4: A(a,b,c) B(a,b,c) C(a,b,c) D(a,b,c) E(a,b,c)
5: A(a,b,) B(a,b,) C(a,b,) D(a,b,)
// The GCC ", ## __VA_ARGS__" extension swallows the comma when followed by
// empty __VA_ARGS__. This extension does not apply in -std=c99 mode, but
// does apply in C++.
//
// GCC: 1: [ ] [ , ] [ ] [ ] [ ]
// GCC: 2: [ a ] [ , a ] [ ,a ] [ a ] [ a ]
// GCC: 3: [ , ] [ , , ] [ ,, ] [ , ] [ ]
// GCC: 4: [ a,b,c ] [ , a,b,c ] [ ,a,b,c ] [ a ,b,c ] [ b,ca ]
// GCC: 5: [ a,b, ] [ , a,b, ] [ ,a,b, ] [ a ,b, ]
// Under C99 standard mode, the GCC ", ## __VA_ARGS__" extension *does not*
// swallow the comma when followed by empty __VA_ARGS__.
//
// C99: 1: [ ] [ , ] [ , ] [ ] [ ]
// C99: 2: [ a ] [ , a ] [ ,a ] [ a ] [ a ]
// C99: 3: [ , ] [ , , ] [ ,, ] [ , ] [ ]
// C99: 4: [ a,b,c ] [ , a,b,c ] [ ,a,b,c ] [ a ,b,c ] [ b,ca ]
// C99: 5: [ a,b, ] [ , a,b, ] [ ,a,b, ] [ a ,b, ]
// Microsoft's extension is on ", __VA_ARGS__" (without explicit ##) where
// the comma is swallowed when followed by empty __VA_ARGS__.
//
// MS: 1: [ ] [ ] [ ] [ ] [ ]
// MS: 2: [ a ] [ , a ] [ ,a ] [ a ] [ a ]
// MS: 3: [ , ] [ , , ] [ ,, ] [ , ] [ ]
// MS: 4: [ a,b,c ] [ , a,b,c ] [ ,a,b,c ] [ a ,b,c ] [ b,ca ]
// MS: 5: [ a,b, ] [ , a,b, ] [ ,a,b, ] [ a ,b, ]
// FIXME: Item 3(d) in MS output should be [ ] not [ , ]