From af5df36aa343234c945fa6eae30d9bb03551e1a5 Mon Sep 17 00:00:00 2001
From: Teddy <ted.sybil@gmail.com>
Date: Wed, 26 Mar 2014 03:12:31 +0800
Subject: fancy error report

---
 ast.c   |  2 +-
 cibic.l | 28 ++++++++++++++++++++--------
 main.c  | 15 +++++++++++++--
 3 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/ast.c b/ast.c
index 97ab281..b76790e 100644
--- a/ast.c
+++ b/ast.c
@@ -371,7 +371,7 @@ char *cnode_debug_type_repr(CNode *ast) {
     else
     {
         *aptr = '\0';
-        sprintf(buffer, "%s:%s(%d,%d)", type, abuff, 
+        sprintf(buffer, "%s:%s(%d:%d)", type, abuff, 
                 ast->loc.row, ast->loc.col);
     }
     return buffer;
diff --git a/cibic.l b/cibic.l
index e857046..52ba764 100644
--- a/cibic.l
+++ b/cibic.l
@@ -1,11 +1,23 @@
 %{
 #include "cibic.tab.h"
+
 int yycolumn = 1;
-#define YY_USER_ACTION \
-    yylloc.first_line = yylloc.last_line = yylineno; \
-    yylloc.first_column = yycolumn; yylloc.last_column = yycolumn + yyleng - 1; \
-    yycolumn += yyleng;
+char linebuff[1024], *lptr = linebuff;
 
+#define YY_USER_ACTION \
+    do { \
+        yylloc.first_line = yylloc.last_line = yylineno; \
+        yylloc.first_column = yycolumn; yylloc.last_column = yycolumn + yyleng - 1; \
+        yycolumn += yyleng; \
+        memmove(lptr, yytext, yyleng);  \
+        lptr += yyleng; \
+    } while (0);
+
+#define NEW_LINE_USER_ACTION \
+    do { \
+        yycolumn = 1; \
+        lptr = linebuff; \
+    } while (0)
 %}
 
 letter [a-zA-Z_$]
@@ -25,14 +37,14 @@ char ([^\n'\\]|\\.|\\[0-7]+|\\[xX][0-9a-fA-F]+)
 "*/"    BEGIN(INITIAL);
 [^*\n]+   // eat comment in chunks
 "*"       // eat the lone star
-\n      { yycolumn = 1; }
+\n      { NEW_LINE_USER_ACTION; }
 }
 
 <INITIAL>{
 "//"    BEGIN(IN_INLINE_COMMENT);
 }
 <IN_INLINE_COMMENT>{
-\n      { yycolumn = 1; BEGIN(INITIAL); }
+\n      { NEW_LINE_USER_ACTION; BEGIN(INITIAL); }
 [^\n]+ 
 }
 
@@ -40,7 +52,7 @@ char ([^\n'\\]|\\.|\\[0-7]+|\\[xX][0-9a-fA-F]+)
 "#"    BEGIN(IN_DIRECTIVE);
 }
 <IN_DIRECTIVE>{
-\n      { yycolumn = 1; BEGIN(INITIAL); }
+\n      { NEW_LINE_USER_ACTION; BEGIN(INITIAL); }
 [^\n]+ 
 }
 
@@ -121,6 +133,6 @@ char ([^\n'\\]|\\.|\\[0-7]+|\\[xX][0-9a-fA-F]+)
 [();,={}\[\]*|\^&<>+\-*//%~!.]              { return *yytext; }
 
 [ \t\r]                                   /* skip whitespaces */
-\n                                          { yycolumn = 1; }
+\n                                          { NEW_LINE_USER_ACTION; }
 .                                           { return UNKNOWN; }
 %%
diff --git a/main.c b/main.c
index 2e6fb35..d36dd6c 100644
--- a/main.c
+++ b/main.c
@@ -4,6 +4,8 @@
 #include "cibic.tab.h"
 #include "ast.h"
 
+extern char linebuff[];
+extern char *lptr;
 extern int yyparse();
 extern FILE *yyin;
 char *fname;
@@ -12,8 +14,17 @@ int yywrap() {
     return 1;
 }
 
-int yyerror(char *s) {
-    fprintf(stderr, "%s\n", s);
+void print_error(char *err_msg, int row, int col) {
+    *lptr = '\0';
+    fprintf(stderr, "%d:%d: %s\n%s\n", 
+            row, col, err_msg, linebuff);
+    while (--col) putchar(' ');
+    putchar('^');
+}
+
+int yyerror(char *err_msg) {
+    print_error(err_msg, 
+            yylloc.first_line, yylloc.first_column);
     return 0;
 }
 
-- 
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