Some more changes for MacOS.

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Some more changes for MacOS.

aclocal.m4:
	Define a macro MERCURY_CHECK_CC_NEEDS_CPP_PRECOMP,
	to check whether we need to append `-traditional-cpp' to $CC.

configure.in:
bindist/bindist.configure.in:
	Use the new macro.

README.MacOS:
	Update the documentation: users don't need to configure using
	`--with-cc="cc --traditional-cpp"' any more.

README.MacOS

@@ -4,16 +4,16 @@ i.e. the "powerpc-apple-darwin" configuration.
 The version of tar in /usr/bin/tar on MacOS (10.1) doesn't work properly --
 it truncates long path names.  Make sure you use GNU tar, which is available
 in /sw/bin/gtar, when unpacking the Mercury source or binary distributions.
+(Also, make sure to use GNU tar if/when *building* such distributions!)
 
 Apple's version of gcc includes support for precompiled headers.
 Unfortunately this support seems to be somewhat buggy, causing it
 to sometimes crash with mysterious errors when building Mercury.
 Furthermore, for the kinds of C code that the Mercury compiler generates,
 it results in a very big slow-down, rather than any speedup.
-So you should use `--traditional-cpp' to disable the use of the
-new ``smart'' [sic] preprocessor.  Configure with
-
-	sh configure --with-cc="cc --traditional-cpp"
+Fortunately this can be disabled by using the --traditional-cpp option.
+The Mercury configure script should enable this option automatically
+if it is needed.
 
 The configure script will by default choose grade reg.gc.
 You can get better performance by using the hlc.gc grade.

aclocal.m4

@@ -13,6 +13,34 @@
 #
 #-----------------------------------------------------------------------------#
 #
+# Turn off MacOS's so-called "smart" C preprocessor, if present,
+# since it causes lots of spurious warning messages,
+# and furthermore it takes way too long and uses way too much memory
+# when preprocessing the C code generated by the Mercury compiler's LLDS
+# back-end.
+#
+AC_DEFUN(MERCURY_CHECK_CC_NEEDS_TRAD_CPP,
+[
+AC_REQUIRE([AC_PROG_CC])
+AC_MSG_CHECKING(whether C compiler need --traditional-cpp)
+AC_CACHE_VAL(mercury_cv_cpp_precomp, [
+	>conftest.c
+	if	test "$GCC" = yes &&
+		$CC -v -c conftest.c 2>&1 | \
+			grep "cpp-precomp.*-smart" > /dev/null
+	then
+		mercury_cv_cpp_precomp=yes
+	else
+		mercury_cv_cpp_precomp=no
+	fi
+])
+AC_MSG_RESULT($mercury_cv_cpp_precomp)
+if test $mercury_cv_cpp_precomp = yes; then
+	CC="$CC --traditional-cpp"
+fi
+])
+#-----------------------------------------------------------------------------#
+#
 # Check for readline and related header files and libraries
 #
 AC_DEFUN(MERCURY_CHECK_READLINE,

bindist/bindist.configure.in

@@ -204,6 +204,7 @@ AC_MSG_RESULT($mercury_cv_asm_does_full_preprocessing)
 AC_SUBST(AS)
 #-----------------------------------------------------------------------------#
 AC_PROG_CC
+MERCURY_CHECK_CC_NEEDS_TRAD_CPP
 AC_SUBST(CC)
 #-----------------------------------------------------------------------------#
 # Microsoft.NET configuration (the bindist may be installed on a machine

configure.in

@@ -339,6 +339,7 @@ esac
 AC_DEFINE_UNQUOTED(MR_HOSTNAMECMD, "$HOSTNAMECMD")
 #-----------------------------------------------------------------------------#
 AC_PROG_CC
+MERCURY_CHECK_CC_NEEDS_TRAD_CPP
 AC_SUBST(CC)
 
 # AC_PROG_CC sets GCC to yes if $CC is GNU C.