Add useful error handler

include/Defs.h

@@ -68,6 +68,7 @@ enum TokenTypes {
     LI_INT,         // Integer literal
     LI_STR,         // String literal
     LI_SEMIC,       // ;
+    LI_COLON,       // :
 
     LI_LBRAC,       // {
     LI_RBRAC,       // }
@@ -93,6 +94,10 @@ enum TokenTypes {
     KW_BREAK,       // "break" keyword
     KW_CONTINUE,    // "continue" keyword
 
+    KW_SWITCH,      // "switch" keyword
+    KW_DEFAULT,     // "default" keyword
+    KW_CASE,        // "case" keyword
+
     KW_PRINT,
     KW_IF,
     KW_ELSE,
@@ -180,6 +185,10 @@ enum SyntaxOps {
     OP_FUNC = 40,       // Define a function
     OP_BREAK,           // Break out of the loop
     OP_CONTINUE,        // Continue the loop
+
+    OP_SWITCH,          // Switch statement
+    OP_DEFAULT,         // Default case
+    OP_CASE = 45        // Case
 };
 
 
@@ -269,14 +278,14 @@ struct FileData {
     // The filename of the assembled object code
     char* ObjectName;
 
-    // The full contents of the source file
-    char* Content;
     // The line of the file we are currently working on, -1 if it is finished
     long CurrentLine;
     // The column of the file we are currently working on, -1 if it is finished
     long CurrentColumn;
     // The depth of the loop currently being parsed.
     long CurrentLoopDepth;
+    // The column that was last marked as "valid", the start of the error block if something goes wrong.
+    long CurrentSafeColumn;
 
     // The symbol currently being lexed - TokenTypes index and integer value.
     struct Token CurrentSymbol;
@@ -508,6 +517,10 @@ void DieChar(char* Error, int Char);
 
 void DieBinary(char* Error, int Number);
 
+void ErrorReport(char* message, ...);
+
+void Safe();
+
 
 /* * * * * * * * * * * * * * * * * * * * * * * * * * * *
  * * * *     C O D E     G E N E R A T I O N     * * * *
@@ -571,6 +584,8 @@ struct AssemblerVtable {
     // Loops and jumps
     int (*AsIf)(struct ASTNode*, int, int);
     int (*AsWhile)(struct ASTNode*);
+    int (*AsSwitch)(struct ASTNode*);
+    int (*AsSwitchTable)(int, int, int, int*, int*, int);
     int (*NewLabel)();
     void (*AsJmp)(int);
     void (*AsLabel)(int);
@@ -619,5 +634,7 @@ struct ASTNode* WhileStatement();
 
 struct ASTNode* ForStatement();
 
+struct ASTNode* SwitchStatement();
+
 
 void DumpTree(struct ASTNode* node, int level);

src/Errors.c

@@ -0,0 +1,84 @@
+/*************/
+/*GEMWIRE    */
+/*    ERYTHRO*/
+/*************/
+#include <stdio.h>
+#include <Defs.h>
+#include <Data.h>
+#include <stdarg.h>
+
+void Safe() {
+    CurrentFile->CurrentSafeColumn = CurrentFile->CurrentColumn;
+}
+
+void printLine(FILE* file, int ln) {
+    char buffer[256];
+    fgets(buffer, 256, file);
+    // Line number
+    printf("%03d|%s", ln + 1, buffer);
+}
+
+void printErrorLine(FILE* file, int ln) {
+    char firstBuffer[256], problemBuffer[256], tailBuffer[256];
+    if (CurrentFile->CurrentSafeColumn != 0)
+        fgets(firstBuffer, CurrentFile->CurrentSafeColumn, file);
+    fgets(problemBuffer, (CurrentFile->CurrentColumn > CurrentFile->CurrentSafeColumn ? CurrentFile->CurrentColumn - CurrentFile->CurrentSafeColumn : CurrentFile->CurrentSafeColumn), file);
+    if (CurrentFile->CurrentColumn > CurrentFile->CurrentSafeColumn)
+        fgets(tailBuffer, 256, file);
+    // Line number
+    printf("%03d|%s\033[0;31m%s\033[0m%s", ln + 1, firstBuffer, problemBuffer, tailBuffer);
+}
+
+void printHelpLine(int line, char* message) {
+    printf("   | %s", message);
+}
+
+void ErrorReport(char* message, ...) {
+    char strbuf[256];
+
+    // Resolve varargs to a string
+    va_list args;
+    va_start(args, message);
+    vsprintf(strbuf, message, args);
+    va_end(args);
+
+    int line = CurrentFile->CurrentLine - 1;
+    FILE* file = fopen(CurrentFile->SourceName, "r");
+
+    int errorOnLastLine = CurrentFile->CurrentColumn == 0;
+
+    // Print context for the error - up to 2 lines above the error
+    if (line < 3) {
+        // If we're at 0 or 1, we need to be careful to not try to print -1 for example.
+        for (int i = 0; i < line; i++)
+            printLine(file, i);
+    } else {
+        // Skip to line - 2
+        char buffer[256];
+        int count = 0;
+        while (count < line - (errorOnLastLine ? 3 : 2)) {
+            fgets(buffer, 256, file);
+            count++;
+        }
+
+        if (errorOnLastLine)
+            printLine(file, line - 3);
+
+        printLine(file, line - 2);
+        if (!errorOnLastLine) printLine(file, line - 1);
+    }
+
+    if (errorOnLastLine) {
+        printErrorLine(file, line - 1);
+        printHelpLine(line, strbuf);
+        printLine(file, line);
+        printLine(file, line + 1);
+    } else {
+        printErrorLine(file, line);
+        printHelpLine(line, strbuf);
+        printLine(file, line + 1);
+        printLine(file, line + 2);
+    }
+
+
+}

src/Lexer.c

@@ -45,8 +45,12 @@ static int NextChar(void) {
 
     Char = fgetc(CurrentFile->Stream);
 
-    if (Char == '\n')
+    CurrentFile->CurrentColumn++;
+
+    if (Char == '\n') {
         CurrentFile->CurrentLine++;
+        CurrentFile->CurrentColumn = 0;
+    }
 
     return Char;
 }
@@ -94,7 +98,7 @@ void VerifyToken(int Type, char* TokenExpected) {
     if (CurrentFile->CurrentSymbol.type == Type)
         Tokenise();
     else {
-        printf("Expected %s on line %ld\n", TokenExpected, CurrentFile->CurrentLine);
+        ErrorReport("Expected %s, but got %s instead.\n", TokenExpected, TokenNames[CurrentFile->CurrentSymbol.type]);
         exit(1);
     }
 }
@@ -298,9 +302,15 @@ static int ReadKeyword(char* Str) {
                 return TY_CHAR;
             if (!strcmp(Str, "continue"))
                 return KW_CONTINUE;
+            if (!strcmp(Str, "case"))
+                return KW_CASE;
                 
             break;
 
+        case 'd':
+            if (!strcmp(Str, "default"))
+                return KW_DEFAULT;
+
         case 'e':
             if (!strcmp(Str, "else"))
                 return KW_ELSE;
@@ -354,6 +364,8 @@ static int ReadKeyword(char* Str) {
         case 's':
             if (!strcmp(Str, "struct"))
                 return KW_STRUCT;
+            if (!strcmp(Str, "switch"))
+                return KW_SWITCH;
             break;
 
         case 'u':