[LLVMbugs] [Bug 4513] New: Builtin::BIalloca not defined under MSVC

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4513

           Summary: Builtin::BIalloca not defined under MSVC
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Keywords: build-problem, portability
          Severity: normal
          Priority: P2
         Component: Basic
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: abbeyj at gmail.com
                CC: llvmbugs at cs.uiuc.edu


When compiling under MSVC, Builtin::BIalloca is not declared.  This causes
CGBuiltin.cpp to fail to compile.

The problem is that the system headers have this:
#if     !__STDC__
/* Non-ANSI names for compatibility */
#define alloca  _alloca
#endif  /* __STDC__*/


When Builtin.h #includes Builtins.def it does so with BUILTIN defined as:
#define BUILTIN(ID, TYPE, ATTRS) BI##ID,


LIBBUILTIN is not defined so Builtins.def supplies a default definition:
#if defined(BUILTIN) && !defined(LIBBUILTIN)
#  define LIBBUILTIN(ID, TYPE, ATTRS, HEADER) BUILTIN(ID, TYPE, ATTRS)
#endif


Then the line
LIBBUILTIN(alloca, "v*z",         "f",     "stdlib.h")

expands to |BI_alloca,| instead of the intended |BIalloca,|

This happens because LIBBUILTIN is defined in terms of BUILTIN.  The
preprocessor rescans and expands the parameter before the concat.  If the line
was |BUILTIN(alloca, ...)| then it would work properly.

Any of the following should fix this:
1) Explicitly #undef alloca
2) Change Builtins.h to explictly #define LIBBUILTIN and remove the default
definition from Builtins.def
3) Change the default definition in Builtins.def to:
#  define LIBBUILTIN(ID, TYPE, ATTRS, HEADER) BUILTIN(##ID, TYPE, ATTRS)
but this isn't portable.  I don't know if there's a portable way to stop the
preprocessor from rescanning.


-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.