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__".

llvm-svn: 167613

1 files changed, 64 insertions, 0 deletions

diff --git a/clang/test/Preprocessor/macro_fn_comma_swallow2.c b/clang/test/Preprocessor/macro_fn_comma_swallow2.c
new file mode 100644
index 00000000000..93ab2b83664
--- /dev/null
+++ b/clang/test/Preprocessor/macro_fn_comma_swallow2.c
@@ -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 [ , ]