Bug 1269171 - Change how mozalloc.h is hooked in STL wrappers. r=froydnj

Since the introduction of the STL wrappers, they have included
mozalloc.h, and multiple times, we've hit header reentrancy problems,
and worked around them as best as we could.

Taking a step back, all mozalloc.h does is:
- declare moz_* allocator functions.
- define inline implementations of various operator new/delete variants.

The first only requires the functions to be declared before they are used,
so mozalloc.h only needs to be included before anything that would use
those functions.

The second doesn't actually require a specific order, as long as the
declaration for those functions comes before their use, and they are
either declared in <new> or implicitly by the C++ compiler.

So all in all, it doesn't matter that mozalloc.h is included before the
wrapped STL headers. What matters is that it's included when STL headers
are included. So arrange things such that mozalloc.h is included after
the first wrapped STL header is fully preprocessed (and all its includes
have been included).

Author: glandium

config/gcc-stl-wrapper.template.h

@@ -17,21 +17,34 @@
 // Silence "warning: #include_next is a GCC extension"
 #pragma GCC system_header
 
+#if defined(DEBUG) && !defined(_GLIBCXX_DEBUG)
+// Enable checked iterators and other goodies
+//
+// FIXME/bug 551254: gcc's debug STL implementation requires -frtti.
+// Figure out how to resolve this with -fno-rtti.  Maybe build with
+// -frtti in DEBUG builds?
+//
+//  # define _GLIBCXX_DEBUG 1
+#endif
+
 // Don't include mozalloc for cstdlib. See bug 1245076.
 #ifndef moz_dont_include_mozalloc_for_cstdlib
 #  define moz_dont_include_mozalloc_for_cstdlib
 #endif
-#ifndef moz_dont_include_mozalloc_for_${HEADER}
-// mozalloc.h wants <new>; break the cycle by always explicitly
-// including <new> here.  NB: this is a tad sneaky.  Sez the gcc docs:
-//
-//    `#include_next' does not distinguish between <file> and "file"
-//    inclusion, nor does it check that the file you specify has the
-//    same name as the current file. It simply looks for the file
-//    named, starting with the directory in the search path after the
-//    one where the current file was found.
-#  include_next <new>
 
+// Include mozalloc after the STL header and all other headers it includes
+// have been preprocessed.
+#if !defined(MOZ_INCLUDE_MOZALLOC_H) && \
+    !defined(moz_dont_include_mozalloc_for_${HEADER})
+#  define MOZ_INCLUDE_MOZALLOC_H
+#  define MOZ_INCLUDE_MOZALLOC_H_FROM_${HEADER}
+#endif
+
+#pragma GCC visibility push(default)
+#include_next <${HEADER}>
+#pragma GCC visibility pop
+
+#ifdef MOZ_INCLUDE_MOZALLOC_H_FROM_${HEADER}
 // See if we're in code that can use mozalloc.  NB: this duplicates
 // code in nscore.h because nscore.h pulls in prtypes.h, and chromium
 // can't build with that being included before base/basictypes.h.
@@ -40,23 +53,8 @@
 #  else
 #    error "STL code can only be used with infallible ::operator new()"
 #  endif
-
-#endif
-
-#if defined(DEBUG) && !defined(_GLIBCXX_DEBUG)
-// Enable checked iterators and other goodies
-//
-// FIXME/bug 551254: gcc's debug STL implementation requires -frtti.
-// Figure out how to resolve this with -fno-rtti.  Maybe build with
-// -frtti in DEBUG builds?
-//
-//  # define _GLIBCXX_DEBUG 1
 #endif
 
-#pragma GCC visibility push(default)
-#include_next <${HEADER}>
-#pragma GCC visibility pop
-
 // gcc calls a __throw_*() function from bits/functexcept.h when it
 // wants to "throw an exception".  functexcept exists nominally to
 // support -fno-exceptions, but since we'll always use the system

config/make-stl-wrappers.py

@@ -30,7 +30,6 @@ def main(outdir, compiler, template_file, header_list_file):
         os.mkdir(outdir)
 
     template = open(template_file, 'r').read()
-    path_to_new = header_path('new', compiler)
 
     for header in open(header_list_file, 'r'):
         header = header.rstrip()
@@ -40,8 +39,7 @@ def main(outdir, compiler, template_file, header_list_file):
         path = header_path(header, compiler)
         with FileAvoidWrite(os.path.join(outdir, header)) as f:
             f.write(string.Template(template).substitute(HEADER=header,
-                                                         HEADER_PATH=path,
-                                                         NEW_HEADER_PATH=path_to_new))
+                                                         HEADER_PATH=path))
 
 
 if __name__ == '__main__':

config/msvc-stl-wrapper.template.h

@@ -8,35 +8,23 @@
 #ifndef mozilla_${HEADER}_h
 #define mozilla_${HEADER}_h
 
-#ifndef MOZ_HAVE_INCLUDED_ALLOC
-#define MOZ_HAVE_INCLUDED_ALLOC
-
 #if _HAS_EXCEPTIONS
 #  error "STL code can only be used with -fno-exceptions"
 #endif
 
+// Include mozalloc after the STL header and all other headers it includes
+// have been preprocessed.
+#if !defined(MOZ_INCLUDE_MOZALLOC_H)
+#  define MOZ_INCLUDE_MOZALLOC_H
+#  define MOZ_INCLUDE_MOZALLOC_H_FROM_${HEADER}
+#endif
+
 // Code built with !_HAS_EXCEPTIONS calls std::_Throw(), but the win2k
 // CRT doesn't export std::_Throw().  So we define it.
 #ifndef mozilla_Throw_h
 #  include "mozilla/throw_msvc.h"
 #endif
 
-// Code might include <new> before other wrapped headers, but <new>
-// includes <exception> and so we want to wrap it.  But mozalloc.h
-// wants <new> also, so we break the cycle by always explicitly
-// including <new> here.
-#include <${NEW_HEADER_PATH}>
-
-// See if we're in code that can use mozalloc.  NB: this duplicates
-// code in nscore.h because nscore.h pulls in prtypes.h, and chromium
-// can't build with that being included before base/basictypes.h.
-#if !defined(XPCOM_GLUE) && !defined(NS_NO_XPCOM) && !defined(MOZ_NO_MOZALLOC)
-#  include "mozilla/mozalloc.h"
-#else
-#  error "STL code can only be used with infallible ::operator new()"
-#endif
-#endif /* MOZ_HAVE_INCLUDED_ALLOC */
-
 #ifdef _DEBUG
 // From
 //   http://msdn.microsoft.com/en-us/library/aa985982%28VS.80%29.aspx
@@ -75,4 +63,15 @@
 
 #pragma warning( pop )
 
+#ifdef MOZ_INCLUDE_MOZALLOC_H_FROM_${HEADER}
+// See if we're in code that can use mozalloc.  NB: this duplicates
+// code in nscore.h because nscore.h pulls in prtypes.h, and chromium
+// can't build with that being included before base/basictypes.h.
+#  if !defined(XPCOM_GLUE) && !defined(NS_NO_XPCOM) && !defined(MOZ_NO_MOZALLOC)
+#    include "mozilla/mozalloc.h"
+#  else
+#    error "STL code can only be used with infallible ::operator new()"
+#  endif
+#endif
+
 #endif  // if mozilla_${HEADER}_h

memory/mozalloc/mozalloc.h

@@ -12,10 +12,17 @@
  * https://bugzilla.mozilla.org/show_bug.cgi?id=427099
  */
 
-#include <stdlib.h>
-#include <string.h>
 #if defined(__cplusplus)
 #  include <new>
+// Since libstdc++ 6, including the C headers (e.g. stdlib.h) instead of the
+// corresponding C++ header (e.g. cstdlib) can cause confusion in C++ code
+// using things defined there. Specifically, with stdlib.h, the use of abs()
+// in gfx/graphite2/src/inc/UtfCodec.h somehow ends up picking the wrong abs()
+#  include <cstdlib>
+#  include <cstring>
+#else
+#  include <stdlib.h>
+#  include <string.h>
 #endif
 
 #if defined(__cplusplus)