diff mbox series

[committed] : C++: -Wwrite-strings: use location of string constant

Message ID 1534545800-5614-1-git-send-email-dmalcolm@redhat.com
State New
Headers show
Series [committed] : C++: -Wwrite-strings: use location of string constant | expand

Commit Message

David Malcolm Aug. 17, 2018, 10:43 p.m. UTC 
Consider:

extern int callee (const char *one, char *two, const char *three);

int test ()
{
  return callee ("first", "second", "third");
}

for which -Wwrite-strings was emitting:

Wwrite-strings.C: In function 'int test()':
Wwrite-strings.C:10:44: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
10 |   return callee ("first", "second", "third");
   |                                            ^

This patch fixes the warning so that it underlines the pertinent argument
at the callsite:

Wwrite-strings.C: In function 'int test()':
Wwrite-strings.C:10:27: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
10 |   return callee ("first", "second", "third");
   |                           ^~~~~~~~

Ideally we ought to also issue a "note" highlighting the pertinent
parameter within the decl, but that's not readily available, so I'm
saving it for another patch.

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.

Committed to trunk as r263635.

gcc/cp/ChangeLog:
	* typeck.c (string_conv_p): Extract location from EXP and use it
	in preference to input_location when issuing warnings.

gcc/testsuite/ChangeLog:
	* g++.dg/conversion/Wwrite-strings.C: New test.
---
 gcc/cp/typeck.c                                  | 10 ++++++----
 gcc/testsuite/g++.dg/conversion/Wwrite-strings.C | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/conversion/Wwrite-strings.C
diff mbox series

Patch

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 64b3d58..8c13ae9 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -2208,6 +2208,8 @@  string_conv_p (const_tree totype, const_tree exp, int warn)
       && !same_type_p (t, wchar_type_node))
     return 0;
 
+  location_t loc = EXPR_LOC_OR_LOC (exp, input_location);
+
   STRIP_ANY_LOCATION_WRAPPER (exp);
 
   if (TREE_CODE (exp) == STRING_CST)
@@ -2230,13 +2232,13 @@  string_conv_p (const_tree totype, const_tree exp, int warn)
   if (warn)
     {
       if (cxx_dialect >= cxx11)
-	pedwarn (input_location, OPT_Wwrite_strings,
+	pedwarn (loc, OPT_Wwrite_strings,
 		 "ISO C++ forbids converting a string constant to %qT",
 		 totype);
       else
-	warning (OPT_Wwrite_strings,
-		 "deprecated conversion from string constant to %qT",
-		 totype);
+	warning_at (loc, OPT_Wwrite_strings,
+		    "deprecated conversion from string constant to %qT",
+		    totype);
     }
 
   return 1;
diff --git a/gcc/testsuite/g++.dg/conversion/Wwrite-strings.C b/gcc/testsuite/g++.dg/conversion/Wwrite-strings.C
new file mode 100644
index 0000000..f6dbb15
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/Wwrite-strings.C
@@ -0,0 +1,24 @@ 
+// { dg-options "-fdiagnostics-show-caret" }
+
+/* Verify that -Wwrite-strings underlines the string literal in question.  */
+
+extern int callee (const char *one, char *two, const char *three);
+
+int test_1 ()
+{
+  return callee ("first", "second", "third"); // { dg-warning "string constant to 'char\\*'" }
+  /* { dg-begin-multiline-output "" }
+   return callee ("first", "second", "third");
+                           ^~~~~~~~
+     { dg-end-multiline-output "" } */
+  // TODO: underline the pertinent param in the decl of callee
+}
+
+char *test_2 (void)
+{
+  return "foo"; // { dg-warning "string constant to 'char\\*'" }
+  /* { dg-begin-multiline-output "" }
+   return "foo";
+          ^~~~~
+     { dg-end-multiline-output "" } */
+}