Document environment variables we handle, and don't mention -pipe (it

isn't yet supported... lazy developers).

llvm-svn: 71109

Author: ddunbar

clang/docs/tools/clang.pod

@@ -179,11 +179,6 @@ Pass I<arg> to the preprocessor.
 
 Write output to I<file>.
 
-=item B<-pipe>
-
-FIXME: WHY DOCUMENT THIS.
-Use pipes between commands, when possible.
-
 =item B<-print-file-name>=I<file>
 
 Print the full library path of I<file>.
@@ -263,14 +258,41 @@ Treat subsequent input files as having type I<language>.
 
 =head1 ENVIRONMENT
 
-No environment variables read.
+=over
+
+=item B<TMPDIR>, B<TEMP>, B<TMP>
+
+These environment variables are checked, in order, for the location to
+write temporary files used during the compilation process.
+
+=item B<CPATH>
+
+If this environment variable is present, it is treated as a delimited
+list of paths to be added to the default system include path list. The
+delimiter is the platform dependent delimitor, as used in the I<PATH>
+environment variable.
+
+Empty components in the environment variable are ignored.
+
+=item B<C_INCLUDE_PATH>, B<OBJC_INCLUDE_PATH>, B<CPLUS_INCLUDE_PATH>,
+B<OBJCPLUS_INCLUDE_PATH>
+
+These environment variables specify additional paths, as for CPATH,
+which are only used when processing the appropriate language.
+
+=item B<MACOSX_DEPLOYMENT_TARGET> (Apple only)
+
+If -mmacosx-version-min is unspecified, the default deployment target
+is read from this environment variable.
+
+=back
 
 =head1 BUGS
 
 Clang currently does not have C++ support, and this manual page is incomplete.
 To report bugs, please visit L<http://llvm.org/bugs/>.  Most bug reports should
-include preprocessed source files (use the B<-E> option) along with information
-to reproduce.
+include preprocessed source files (use the B<-E> option) and the full output of 
+the compiler, along with information to reproduce.
 
 =head1 SEE ALSO