* tm.texi: Document STDC_0_IN_SYSTEM_HEADERS.

From-SVN: r43426

gcc/ChangeLog

+2001-06-17  Neil Booth  <neil@daikokuya.demon.co.uk>
+
+	* tm.texi: Document STDC_0_IN_SYSTEM_HEADERS.
+
 Sat Jun 16 20:20:39 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 
 	* expr.c (expand_expr, case ADDR_EXPR): If taking address of SAVE_EXPR,

gcc/doc/tm.texi

@@ -8080,6 +8080,18 @@ The default definition of this macro is 64 plus 8 times the number of
 arguments that the function accepts.  Some people think a larger
 threshold should be used on RISC machines.
 
+@findex STDC_0_IN_SYSTEM_HEADERS
+@item STDC_0_IN_SYSTEM_HEADERS
+In normal operation, the preprocessor expands @code{__STDC__} to the
+constant 1, to signify that GCC conforms to ISO Standard C@.  On some
+hosts, like Solaris, the system compiler uses a different convention,
+where @code{__STDC__} is normally 0, but is 1 if the user specifies
+strict conformance to the C Standard.
+
+Defining @code{STDC_0_IN_SYSTEM_HEADERS} makes GNU CPP follows the host
+convention when processing system header files, but when processing user
+files @code{__STDC__} will always expand to 1.
+
 @findex SCCS_DIRECTIVE
 @item SCCS_DIRECTIVE
 Define this if the preprocessor should ignore @code{#sccs} directives