MFC r265829 (by imp):

  Support, to the extent we generate proper command lines, compiling
  with clang 3.3. Useful for test building -current on a -stable system
  in individual directories. Potentially useful if we ever want to
  support, say, gcc 4.8 or 4.9's new warnings when building with an
  external toolchain (but such support not yet committed). Document
  the bsd.compiler.mk interface.

MFC r266587 (by imp):
  Allow CC to not actually exist. During the ports INDEX run, all the
  Makefiles are evaluated without building things. In a normal build,
  the prerequisites would be built, and CC would be an actual thing. In
  an INDEX build, though, they don't exists. Redirect stderr to get rid
  of annoying messages, and assume that the compiler version is 0 if the
  actual compiler can't tell us. Do this in preference to guessing based
  on numbers because gcc410 might be 4.10, or 4.1.0 and without
  carefully crafted special knowledge we differentiate between them
  easily (also ming-gcc has no clues at all). Elsewhere, don't trust
  the compiler version if it is 0.

MFC r273405 (by bapt):
  When using an external toolchain note that gcc 4.8+ supports C++11

  Submitted by:	imp

MFC r275557 (by ngie):
  Fix typos in comments and wrap to <80 columns

MFC r275588 (by ngie):
  ${CC} --version doesn't need to be queried if both COMPILER_TYPE and
  COMPILER_VERSION are known

MFC r275589 (by ngie):
  The previous commit should have been a logical or not a logical "and"

  Pointyhat to: me

2 files changed, 41 insertions, 12 deletions

diff --git a/share/mk/bsd.compiler.mk b/share/mk/bsd.compiler.mk
index 2d648de..511d377 100644
--- a/share/mk/bsd.compiler.mk
+++ b/share/mk/bsd.compiler.mk
@@ -1,26 +1,52 @@
 # $FreeBSD$
 
+# Setup variables for the compiler
+#
+# COMPILER_TYPE is the major type of compiler. Currently gcc and clang support
+# automatic detection. Other compiler types can be shoe-horned in, but require
+# explicit setting of the compiler type. The compiler type can also be set
+# explicitly if, say, you install gcc as clang...
+#
+# COMPILER_VERSION is a numeric constant equal to:
+#     major * 10000 + minor * 100 + tiny
+# It too can be overriden on the command line. When testing it, be sure to
+# make sure that you are limiting the test to a specific compiler. Testing
+# against 30300 for gcc likely isn't  what you wanted (since versions of gcc
+# prior to 4.2 likely have no prayer of working).
+#
+# COMPILER_FEATURES will contain one or more of the following, based on
+# compiler support for that feature:
+#
+# - c++11 : supports full (or nearly full) C++11 programming environment.
+#
+# This file may be included multiple times, but only has effect the first time.
+#
+
+.if !defined(COMPILER_TYPE) || !defined(COMPILER_VERSION)
+_v!=	${CC} --version 2>/dev/null || echo 0.0.0
 .if !defined(COMPILER_TYPE)
-. if ${CC:T:Mgcc*}
+. if ${CC:T:M*gcc*}
 COMPILER_TYPE:=	gcc  
-. elif ${CC:T:Mclang}
+. elif ${CC:T:M*clang*}
 COMPILER_TYPE:=	clang
-. else
-_COMPILER_VERSION!=	${CC} --version
-.  if ${_COMPILER_VERSION:Mgcc}
+. elif ${_v:Mgcc}
 COMPILER_TYPE:=	gcc
-.  elif ${_COMPILER_VERSION:M\(GCC\)}
+. elif ${_v:M\(GCC\)}
 COMPILER_TYPE:=	gcc
-.  elif ${_COMPILER_VERSION:Mclang}
+. elif ${_v:Mclang}
 COMPILER_TYPE:=	clang
-.  else
+. else
 .error Unable to determine compiler type for ${CC}.  Consider setting COMPILER_TYPE.
-.  endif
-.  undef _COMPILER_VERSION
 . endif
 .endif
+.if !defined(COMPILER_VERSION)
+COMPILER_VERSION!=echo ${_v:M[1-9].[0-9]*} | awk -F. '{print $$1 * 10000 + $$2 * 100 + $$3;}'
+.endif
+.undef _v
+.endif
 
-.if ${COMPILER_TYPE} == "clang"
+.if ${COMPILER_TYPE} == "clang" || \
+	(${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} >= 40800)
 COMPILER_FEATURES=	c++11
 .else
 COMPILER_FEATURES=
diff --git a/share/mk/bsd.sys.mk b/share/mk/bsd.sys.mk
index 3428edc..9ac01f4 100644
--- a/share/mk/bsd.sys.mk
+++ b/share/mk/bsd.sys.mk
@@ -69,7 +69,10 @@ CWARNFLAGS+=	-Wno-pointer-sign
 # is set to low values, these have to be disabled explicitly.
 .if ${COMPILER_TYPE} == "clang" && !defined(EARLY_BUILD)
 .if ${WARNS} <= 6
-CWARNFLAGS+=	-Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable
+CWARNFLAGS+=	-Wno-empty-body -Wno-string-plus-int
+.if ${COMPILER_VERSION} > 30300
+CWARNFLAGS+=	-Wno-unused-const-variable
+.endif
 .endif # WARNS <= 6
 .if ${WARNS} <= 3
 CWARNFLAGS+=	-Wno-tautological-compare -Wno-unused-value\