PR preprocessor/16192

	PR preprocessor/15913
	PR preprocessor/15572
	* cppexp.c (_cpp_parse_expr): Handle remaining cases where an
	expression is missing.
	* cppinit.c (post_options): Traditional cpp doesn't do // comments.
	* doc/cpp.texi: Don't document what we do for ill-formed expressions.
	* doc/cppopts.texi: Clarify processing of command-line defines.

testsuite:
	* gcc.dg/cpp/if-mop.c: Two new testcases.
	* gcc.dg/cpp/trad/comment-3.c: New.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-3_4-branch@83813 138bc75d-0d04-0410-961f-82ee72b054a4

6 files changed, 34 insertions, 15 deletions

diff --git a/gcc/cppexp.c b/gcc/cppexp.c
index 5603f5bd58a..cb35b6c782f 100644
--- a/gcc/cppexp.c
+++ b/gcc/cppexp.c
@@ -745,18 +745,22 @@ _cpp_parse_expr (cpp_reader *pfile)
 	}
       else if (want_value)
 	{
-	  /* Ordering here is subtle and intended to favor the
-	     missing parenthesis diagnostics over alternatives.  */
-	  if (op.op == CPP_CLOSE_PAREN)
-	    {
-	      if (top->op == CPP_OPEN_PAREN)
-		SYNTAX_ERROR ("void expression between '(' and ')'");
-	    }
-	  else if (top->op == CPP_EOF)
+	  /* We want a number (or expression) and haven't got one.
+	     Try to emit a specific diagnostic.  */
+	  if (op.op == CPP_CLOSE_PAREN && top->op == CPP_OPEN_PAREN)
+	    SYNTAX_ERROR ("missing expression between '(' and ')'");
+
+	  if (op.op == CPP_EOF && top->op == CPP_EOF)
 	    SYNTAX_ERROR ("#if with no expression");
+
 	  if (top->op != CPP_EOF && top->op != CPP_OPEN_PAREN)
 	    SYNTAX_ERROR2 ("operator '%s' has no right operand",
 			   cpp_token_as_text (pfile, top->token));
+	  else if (op.op == CPP_CLOSE_PAREN || op.op == CPP_EOF)
+	    /* Complain about missing paren during reduction.  */;
+	  else
+	    SYNTAX_ERROR2 ("operator '%s' has no left operand",
+			   cpp_token_as_text (pfile, op.token));
 	}
 
       top = reduce (pfile, top, op.op);
diff --git a/gcc/cppinit.c b/gcc/cppinit.c
index 0776476b0e9..ae30568699c 100644
--- a/gcc/cppinit.c
+++ b/gcc/cppinit.c
@@ -618,6 +618,8 @@ post_options (cpp_reader *pfile)
 
   if (CPP_OPTION (pfile, traditional))
     {
+      CPP_OPTION (pfile, cplusplus_comments) = 0;
+
       /* Traditional CPP does not accurately track column information.  */
       CPP_OPTION (pfile, show_column) = 0;
       CPP_OPTION (pfile, trigraphs) = 0;
diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
index 5d1cb9b3029..8080342b889 100644
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -2960,9 +2960,6 @@ expression, and may give different results in some cases.  If the value
 comes out to be nonzero, the @samp{#if} succeeds and the @var{controlled
 text} is included; otherwise it is skipped.
 
-If @var{expression} is not correctly formed, GCC issues an error and
-treats the conditional as having failed.
-
 @node Defined
 @subsection Defined
 
diff --git a/gcc/doc/cppopts.texi b/gcc/doc/cppopts.texi
index fb8f5c72122..6e784de1f50 100644
--- a/gcc/doc/cppopts.texi
+++ b/gcc/doc/cppopts.texi
@@ -17,10 +17,14 @@ Predefine @var{name} as a macro, with definition @code{1}.
 
 @item -D @var{name}=@var{definition}
 Predefine @var{name} as a macro, with definition @var{definition}.
-There are no restrictions on the contents of @var{definition}, but if
-you are invoking the preprocessor from a shell or shell-like program you
-may need to use the shell's quoting syntax to protect characters such as
-spaces that have a meaning in the shell syntax.
+The contents of @var{definition} are tokenized and processed as if
+they appeared during translation phase three in a @samp{#define}
+directive.  In particular, the definition will be truncated by
+embedded newline characters.
+
+If you are invoking the preprocessor from a shell or shell-like
+program you may need to use the shell's quoting syntax to protect
+characters such as spaces that have a meaning in the shell syntax.
 
 If you wish to define a function-like macro on the command line, write
 its argument list with surrounding parentheses before the equals sign
diff --git a/gcc/testsuite/gcc.dg/cpp/if-mop.c b/gcc/testsuite/gcc.dg/cpp/if-mop.c
index 9202740e6b1..119c7392e06 100644
--- a/gcc/testsuite/gcc.dg/cpp/if-mop.c
+++ b/gcc/testsuite/gcc.dg/cpp/if-mop.c
@@ -23,3 +23,9 @@
 
 #if (2) 4 * 2  /* { dg-error "missing bin" "close paren then immediate" } */
 #endif
+
+#if == 2  /* { dg-error "no left op" } */
+#endif
+
+#if (==2)  /* { dg-error "no left op" } */
+#endif
diff --git a/gcc/testsuite/gcc.dg/cpp/trad/comment-3.c b/gcc/testsuite/gcc.dg/cpp/trad/comment-3.c
new file mode 100644
index 00000000000..e2710ad5629
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/trad/comment-3.c
@@ -0,0 +1,6 @@
+/* Test we don't accept C++ comments.  */
+
+/* { dg-do preprocess } */
+
+#if 0
+#endif //  /* { dg-warning "extra tokens" } */