From fa5050d5c73b5acee28999ec2ba44cf1173234b7 Mon Sep 17 00:00:00 2001
From: Matt Pharr <matt.pharr@intel.com>
Date: Mon, 3 Oct 2011 21:09:04 -0700
Subject: [PATCH] Error reporting improvements.

Don't print more than 3 lines of source file context with errors.
  (Any more than that is almost certainly not the Right Thing to do.)
Make some parsing error messages more clear.
---
 parse.yy |  6 +++---
 util.cpp | 11 ++++++++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/parse.yy b/parse.yy
index d51420e5..0013dd9a 100644
--- a/parse.yy
+++ b/parse.yy
@@ -946,7 +946,7 @@ parameter_list
         else {
             std::vector<std::string> alternates = MatchStrings(yytext, builtinTokens);
             std::string alts = lGetAlternates(alternates);
-            Error(@1, "Syntax error--token \"%s\" unknown.%s", yytext, alts.c_str());
+            Error(@1, "Syntax error--token \"%s\" unexpected.%s", yytext, alts.c_str());
         }
         $$ = NULL;
     }
@@ -1050,7 +1050,7 @@ statement
         else {
             std::vector<std::string> alternates = MatchStrings(yytext, builtinTokens);
             std::string alts = lGetAlternates(alternates);
-            Error(@1, "Syntax error--token \"%s\" unknown.%s", yytext, alts.c_str());
+            Error(@1, "Syntax error--token \"%s\" unexpected.%s", yytext, alts.c_str());
         }
         $$ = NULL;
     }
@@ -1209,7 +1209,7 @@ translation_unit
         else {
             std::vector<std::string> alternates = MatchStrings(yytext, builtinTokens);
             std::string alts = lGetAlternates(alternates);
-            Error(@1, "Syntax error--token \"%s\" unknown.%s", yytext, alts.c_str());
+            Error(@1, "Syntax error--token \"%s\" unexpected.%s", yytext, alts.c_str());
         }
     }
     ;
diff --git a/util.cpp b/util.cpp
index 599c2157..36cd83c0 100644
--- a/util.cpp
+++ b/util.cpp
@@ -111,7 +111,10 @@ lPrintFileLineContext(SourcePos p) {
 
     int c, curLine = 1;
     while ((c = fgetc(f)) != EOF) {
-        if (curLine >= p.first_line && curLine <= p.last_line)
+        // Don't print more than three lines of context.  (More than that,
+        // and we're probably doing the wrong thing...)
+        if (curLine >= std::max(p.first_line, p.last_line-2) && 
+            curLine <= p.last_line)
             fputc(c, stderr);
         if (c == '\n')
             ++curLine;
@@ -313,6 +316,12 @@ FatalError(const char *file, int line, const char *message) {
 // http://en.wikipedia.org/wiki/Levenshtein_distance
 int
 StringEditDistance(const std::string &str1, const std::string &str2, int maxDist) {
+    // Small hack: don't return 0 if the strings are the same; if we've
+    // gotten here, there's been a parsing error, and suggesting the same
+    // string isn't going to actually help things.
+    if (str1 == str2)
+        return maxDist;
+
     int n1 = (int)str1.size(), n2 = (int)str2.size();
     int nmax = std::max(n1, n2);