[PATCH] D44604: Make stdarg.h compatible with FreeBSD

[Alexander Richardson via Phabricator via cfe-commits]

arichardson created this revision.
arichardson added reviewers: efriedma, dim.
Herald added subscribers: cfe-commits, krytarowski, sdardis, emaste.

On FreeBSD it is currently not possible to use the clang builtin
headers to build the base system. The build will fail with the
following error if I don't delete the std* headers from the clang
install directory:

  /sources/freebsd-mips/include/stdio.h:72:19: error:
  redefinition of typedef 'va_list' is a C11 feature
  [-Werror,-Wtypedef-redefinition]
  typedef __va_list       va_list;
                          ^
  /home/alr48/cheri/output/sdk/lib/clang/7.0.0/include/stdarg.h:30:27:
  note: previous definition is here
  typedef __builtin_va_list va_list;
  
  /sources/freebsd-mips/sys/sys/_stdarg.h:46:11: error: 'va_start' macro redefined
  [-Werror,-Wmacro-redefined]
    #define       va_start(ap, last)      __builtin_va_start((ap), (last))
                  ^
  /home/alr48/cheri/output/sdk/lib/clang/7.0.0/include/stdarg.h:35:9:
  note: previous definition is here
    #define va_start(ap, param) __builtin_va_start(ap, param)

FreeBSD includes definitions of va_list, va_copy, etc in the
<machine/stdarg.h> header and some files end up including both that
header and <stdarg.h>.

Only defining the va_* macros if they are not yet defined fixes the
macro redefiniton issue and probably also makes sense for other
operating systems. However, for the va_list typedef I can't think
of a better solution than to also check for _VA_LIST_DECLARED and
define it.


Repository:
  rC Clang

https://reviews.llvm.org/D44604

Files:
  lib/Headers/stdarg.h


Index: lib/Headers/stdarg.h
===================================================================
--- lib/Headers/stdarg.h
+++ lib/Headers/stdarg.h
@@ -26,22 +26,33 @@
 #ifndef __STDARG_H
 #define __STDARG_H
 
-#ifndef _VA_LIST
+#if !defined(_VA_LIST) && !defined(_VA_LIST_DECLARED)
 typedef __builtin_va_list va_list;
 #define _VA_LIST
+#define _VA_LIST_DECLARED /* FreeBSD */
 #endif
+#ifndef va_start
 #define va_start(ap, param) __builtin_va_start(ap, param)
+#endif
+#ifndef va_end
 #define va_end(ap)          __builtin_va_end(ap)
+#endif
+#ifndef va_arg
 #define va_arg(ap, type)    __builtin_va_arg(ap, type)
+#endif
 
 /* GCC always defines __va_copy, but does not define va_copy unless in c99 mode
  * or -ansi is not specified, since it was not part of C90.
  */
+#ifndef __va_copy
 #define __va_copy(d,s) __builtin_va_copy(d,s)
+#endif
 
 #if __STDC_VERSION__ >= 199901L || __cplusplus >= 201103L || !defined(__STRICT_ANSI__)
+#ifndef va_copy
 #define va_copy(dest, src)  __builtin_va_copy(dest, src)
 #endif
+#endif
 
 #ifndef __GNUC_VA_LIST
 #define __GNUC_VA_LIST 1


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