diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2935b3274a40c4ca7ddf0a338e1a4d8382a6aa73..d6e62a6cecb50593ecc183e381490c3dcd1f0ecd 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2005-11-03  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c++/17964
+	* diagnostic.c (diagnostic_set_info_translated): New function.
+	(diagnostic_set_info): Use it.  Add comment.
+	* diagnostic.h (diagnostic_set_info_translated): Declare.
+
 2005-11-03  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* dwarf2asm.c (dw2_force_const_mem): Add new parameter 'public'.
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 625413b364f7cbba317346ff70503c06e0543f33..5d281d31361db93149294b702c6a58ff7540bc81 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2005-11-03  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c++/17964
+	* error.c (cp_cpp_error): New function.
+	* cp-tree.h (cp_cpp_error): Declare.
+	* parser.c (cp_lexer_new_main): Set CPP option client_diagnostic
+	and error callback after lexing.
+
 2005-11-03  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/21627
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 97cc064110c7b87ee2981485b013e1ff85cd2106..e1ca9f3bea7a596abe90c927a179799350d6df7d 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -4437,5 +4437,8 @@ extern void cp_genericize			(tree);
 #else
 #define ATTRIBUTE_GCC_CXXDIAG(m, n) ATTRIBUTE_NONNULL(m)
 #endif
+extern void cp_cpp_error			(cpp_reader *, int,
+						 const char *, va_list)
+     ATTRIBUTE_GCC_CXXDIAG(3,0);
 
 #endif /* ! GCC_CP_TREE_H */
diff --git a/gcc/cp/error.c b/gcc/cp/error.c
index 8e39ccadd1e0603c287b217f7b1511be4d53e569..d5144b446f73346a05a870bc77a953b853051482 100644
--- a/gcc/cp/error.c
+++ b/gcc/cp/error.c
@@ -2327,3 +2327,36 @@ cp_printer (pretty_printer *pp, text_info *text, const char *spec,
 #undef next_lang
 #undef next_int
 }
+
+/* Callback from cpp_error for PFILE to print diagnostics arising from
+   interpreting strings.  The diagnostic is of type LEVEL; MSG is the
+   translated message and AP the arguments.  */
+
+void
+cp_cpp_error (cpp_reader *pfile ATTRIBUTE_UNUSED, int level,
+	      const char *msg, va_list ap)
+{
+  diagnostic_info diagnostic;
+  diagnostic_t dlevel;
+  switch (level)
+    {
+    case CPP_DL_WARNING:
+    case CPP_DL_WARNING_SYSHDR:
+      dlevel = DK_WARNING;
+      break;
+    case CPP_DL_PEDWARN:
+      dlevel = pedantic_error_kind ();
+      break;
+    case CPP_DL_ERROR:
+      dlevel = DK_ERROR;
+      break;
+    case CPP_DL_ICE:
+      dlevel = DK_ICE;
+      break;
+    default:
+      gcc_unreachable ();
+    }
+  diagnostic_set_info_translated (&diagnostic, msg, &ap,
+				  input_location, dlevel);
+  report_diagnostic (&diagnostic);
+}
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 9821981f310f43e453226b0fc9cbea2e7c95f774..bbc5c1156bdcff6b4683da2ab4c931fca0667ce2 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -297,6 +297,11 @@ cp_lexer_new_main (void)
      string constant concatenation.  */
   c_lex_return_raw_strings = false;
 
+  /* Subsequent preprocessor diagnostics should use compiler
+     diagnostic functions to get the compiler source location.  */
+  cpp_get_options (parse_in)->client_diagnostic = true;
+  cpp_get_callbacks (parse_in)->error = cp_cpp_error;
+
   gcc_assert (lexer->next_token->type != CPP_PURGED);
   return lexer;
 }
diff --git a/gcc/diagnostic.c b/gcc/diagnostic.c
index c416010b223084052dcee9d184412d610505ec35..7f4d8147340f8f31670314929d61930c29409328 100644
--- a/gcc/diagnostic.c
+++ b/gcc/diagnostic.c
@@ -112,19 +112,31 @@ diagnostic_initialize (diagnostic_context *context)
   context->lock = 0;
 }
 
+/* Initialize DIAGNOSTIC, where the message MSG has already been
+   translated.  */
 void
-diagnostic_set_info (diagnostic_info *diagnostic, const char *gmsgid,
-		     va_list *args, location_t location,
-		     diagnostic_t kind)
+diagnostic_set_info_translated (diagnostic_info *diagnostic, const char *msg,
+				va_list *args, location_t location,
+				diagnostic_t kind)
 {
   diagnostic->message.err_no = errno;
   diagnostic->message.args_ptr = args;
-  diagnostic->message.format_spec = _(gmsgid);
+  diagnostic->message.format_spec = msg;
   diagnostic->location = location;
   diagnostic->kind = kind;
   diagnostic->option_index = 0;
 }
 
+/* Initialize DIAGNOSTIC, where the message GMSGID has not yet been
+   translated.  */
+void
+diagnostic_set_info (diagnostic_info *diagnostic, const char *gmsgid,
+		     va_list *args, location_t location,
+		     diagnostic_t kind)
+{
+  diagnostic_set_info_translated (diagnostic, _(gmsgid), args, location, kind);
+}
+
 /* Return a malloc'd string describing a location.  The caller is
    responsible for freeing the memory.  */
 char *
diff --git a/gcc/diagnostic.h b/gcc/diagnostic.h
index e44d68028ebf085c007bb587edbe8f778e0779ae..3a3204bdcc3599f96b4e313576ca5df3c9931644 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -184,6 +184,10 @@ extern void diagnostic_report_diagnostic (diagnostic_context *,
 #ifdef ATTRIBUTE_GCC_DIAG
 extern void diagnostic_set_info (diagnostic_info *, const char *, va_list *,
 				 location_t, diagnostic_t) ATTRIBUTE_GCC_DIAG(2,0);
+extern void diagnostic_set_info_translated (diagnostic_info *, const char *,
+					    va_list *, location_t,
+					    diagnostic_t)
+     ATTRIBUTE_GCC_DIAG(2,0);
 #endif
 extern char *diagnostic_build_prefix (diagnostic_info *);
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ac49bbcd28a45f136f2c4c6e732b899da8312a92..49d41e153e359b40e0fbe4b939241eed5107b220 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2005-11-03  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c++/17964
+	* g++.dg/cpp/string-1.C: New test.
+
 2005-11-03  Joseph S. Myers  <joseph@codesourcery.com>
 
 	* gcc.target/powerpc: New directory.
diff --git a/gcc/testsuite/g++.dg/cpp/string-1.C b/gcc/testsuite/g++.dg/cpp/string-1.C
new file mode 100644
index 0000000000000000000000000000000000000000..da3133071d73fdc9aaf9a52d1ae085241c7b773f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp/string-1.C
@@ -0,0 +1,9 @@
+// Test location of diagnostics for interpreting strings.  Bug 17964.
+// Origin: Joseph Myers <joseph@codesourcery.com>
+// { dg-do compile }
+
+const char *s = "\q"; // { dg-error "unknown escape sequence" }
+
+const char *t = "\	"; // { dg-error "unknown escape sequence" }
+
+const char *u = "";
diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index 884002b1ea0e6505a503dd9c6480e9fe2e88f47f..c0364802678bf1667851b2b831900d092188d6b3 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,11 @@
+2005-11-03  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c++/17964
+	* include/cpplib.h (struct cpp_options): Add client_diagnostic.
+	(struct cpp_callbacks): Add error.
+	* errors.c (cpp_error): If client_diagnostic, use error callback.
+	* charset.c (convert_escape): Don't use %03o in diagnostic.
+
 2005-10-21  James E Wilson  <wilson@specifix.com>
 
 	PR preprocessor/15220
diff --git a/libcpp/charset.c b/libcpp/charset.c
index 2c87fb6ac279526bae4b1e9a8b5a1414a2a60e4b..78c89816735ac0beab0bc02db904c8421e26ac62 100644
--- a/libcpp/charset.c
+++ b/libcpp/charset.c
@@ -1277,8 +1277,14 @@ convert_escape (cpp_reader *pfile, const uchar *from, const uchar *limit,
 	cpp_error (pfile, CPP_DL_PEDWARN,
 		   "unknown escape sequence '\\%c'", (int) c);
       else
-	cpp_error (pfile, CPP_DL_PEDWARN,
-		   "unknown escape sequence: '\\%03o'", (int) c);
+	{
+	  /* diagnostic.c does not support "%03o".  When it does, this
+	     code can use %03o directly in the diagnostic again.  */
+	  char buf[32];
+	  sprintf(buf, "%03o", (int) c);
+	  cpp_error (pfile, CPP_DL_PEDWARN,
+		     "unknown escape sequence: '\\%s'", buf);
+	}
     }
 
   /* Now convert what we have to the execution character set.  */
diff --git a/libcpp/errors.c b/libcpp/errors.c
index 477101e3041e26118630e0ec9a672d290e2301c0..554d9e3c5f1a7cf2f9c682d99ffa1463b0cd241b 100644
--- a/libcpp/errors.c
+++ b/libcpp/errors.c
@@ -140,20 +140,25 @@ cpp_error (cpp_reader * pfile, int level, const char *msgid, ...)
   
   va_start (ap, msgid);
 
-  if (CPP_OPTION (pfile, traditional))
-    {
-      if (pfile->state.in_directive)
-	src_loc = pfile->directive_line;
-      else
-	src_loc = pfile->line_table->highest_line;
-    }
+  if (CPP_OPTION (pfile, client_diagnostic))
+    pfile->cb.error (pfile, level, _(msgid), ap);
   else
     {
-      src_loc = pfile->cur_token[-1].src_loc;
-    }
+      if (CPP_OPTION (pfile, traditional))
+	{
+	  if (pfile->state.in_directive)
+	    src_loc = pfile->directive_line;
+	  else
+	    src_loc = pfile->line_table->highest_line;
+	}
+      else
+	{
+	  src_loc = pfile->cur_token[-1].src_loc;
+	}
 
-  if (_cpp_begin_message (pfile, level, src_loc, 0))
-    v_message (msgid, ap);
+      if (_cpp_begin_message (pfile, level, src_loc, 0))
+	v_message (msgid, ap);
+    }
 
   va_end (ap);
 }
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 3c4d0d6cb5b452e5ab43424592ddd8425a70b0c1..c5d8e85391a4a4e622e3d8a8e490677c62b450d1 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -435,6 +435,9 @@ struct cpp_options
   /* True means return pragmas as tokens rather than processing
      them directly. */
   bool defer_pragmas;
+
+  /* True means error callback should be used for diagnostics.  */
+  bool client_diagnostic;
 };
 
 /* Callback for header lookup for HEADER, which is the name of a
@@ -467,6 +470,11 @@ struct cpp_callbacks
   int (*valid_pch) (cpp_reader *, const char *, int);
   void (*read_pch) (cpp_reader *, const char *, int, const char *);
   missing_header_cb missing_header;
+
+  /* Called to emit a diagnostic if client_diagnostic option is true.
+     This callback receives the translated message.  */
+  void (*error) (cpp_reader *, int, const char *, va_list)
+       ATTRIBUTE_PRINTF(3,0);
 };
 
 /* Chain of directories to look for include files in.  */