implemented OFFSETOF

Author: totalspectrum

Changelog.txt

@@ -1,3 +1,6 @@
+Version 7.6.7
+- Add OFFSETOF implementation
+
 Version 7.6.6
 - Increase maximum number of files in a .side from 256 to 1024
 - Fix Spin2 ABORT (thanks to Ada)

ast.c

@@ -894,6 +894,7 @@ static const char *astnames[] = {
 
     "namespace",
     "temp_identifier",
+    "offsetof",
 };
 
 //

ast.h

@@ -256,6 +256,7 @@ enum astkind {
 
     AST_NAMESPACE = 185,
     AST_TEMP_IDENTIFIER = 186,
+    AST_OFFSETOF = 187,
 };
 
 /* forward reference */

backends/cpp/cppexpr.c

@@ -1678,6 +1678,15 @@ PrintExpr(Flexbuf *f, AST *expr, int flags)
         PrintExpr(f, expr->left, flags);
         flexbuf_printf(f, ")");
         break;
+    case AST_OFFSETOF:
+        {
+            AST *typ = ExprType(expr->left);
+            const char *fieldname = GetIdentifierName(expr->right);
+            flexbuf_printf(f, "offsetof(");
+            PrintCastType(f, typ);
+            flexbuf_printf(f, ", %s)", fieldname);
+        }
+        break;
 #if 0        
     case AST_VA_START:
         PrintLHS(f, expr->left, flags | PRINTEXPR_ASSIGNMENT);

backends/cpp/outcpp.c

@@ -832,6 +832,9 @@ PrintCppFile(Flexbuf *f, Module *parse)
     if (ModData(parse)->needsString) {
         flexbuf_printf(f, "#include <string.h>\n");
     }
+    if (ModData(parse)->needsOffsetof) {
+        flexbuf_printf(f, "#include <stddef.h>\n");
+    }
     IfdefPropeller(f);
     flexbuf_printf(f, "#define __SPIN2CPP__\n");
     if (gl_p2) {
@@ -953,6 +956,9 @@ SetCppFlags(CppModData *bedata, AST *ast)
     case AST_SPRREF:
         bedata->needsCogAccess = 1;
         break;
+    case AST_OFFSETOF:
+        bedata->needsOffsetof = 1;
+        break;
     case AST_OPERATOR:
         {
             switch (ast->d.ival) {

backends/cpp/outcpp.h

@@ -33,6 +33,7 @@ typedef struct asmmoddata {
     char needsLockFuncs;
     char needsCogAccess;
     char needsCoginit;
+    char needsOffsetof;
 
     /* flags for whether tuples of size N are needed */
     /* if needsTuple & (1<<N) then we need a definition for TupleN__ */

backends/nucode/outnu.c

@@ -2229,6 +2229,7 @@ static void NuCompileStatement(NuIrList *irl, AST *ast) {
     case AST_MEMREF:
     case AST_CONDRESULT:
     case AST_SIZEOF:
+    case AST_OFFSETOF:
         n = NuCompileExpression(irl, ast);
         NuCompileDrop(irl, n);
         break;

expr.c

@@ -1737,6 +1737,35 @@ EvalExpr(AST *expr, unsigned flags, int *valid, int depth)
         }
         return intExpr(TypeSize(typ));
     }
+    case AST_OFFSETOF:
+    {
+        AST *typ = ExprType(expr->left);
+        Module *Q;
+        Symbol *sym;
+        const char *fieldname;
+        if (!typ) {
+            ERROR(expr, "Unknown type for offsetof");
+            return intExpr(0);
+        }
+        typ = RemoveTypeModifiers(typ);
+        if (!IsClassType(typ)) {
+            ERROR(expr, "offsetof requires a struct or union type");
+            return intExpr(0);
+        }
+        Q = GetClassPtr(typ);
+        if (!Q) {
+            ERROR(expr, "Internal error: unable to get class for offsetof");
+            return intExpr(0);
+        }
+        fieldname = GetUserIdentifierName(expr->right);
+        sym = LookupSymbolInTable(&Q->objsyms, fieldname);
+        if (!sym || sym->kind != SYM_VARIABLE) {
+            ERROR(expr, "Unknown field `%s' in offsetof", fieldname);
+            return intExpr(0);
+        }
+        /* For unions all members have offset 0 (already stored in sym->offset) */
+        return intExpr(sym->offset);
+    }
     case AST_FLOAT:
         if (gl_fixedreal) {
             return fixedExpr(expr->d.ival);
@@ -3411,6 +3440,7 @@ ExprTypeRelative(SymbolTable *table, AST *expr, Module *P)
     case AST_NEW:
         return expr->left;
     case AST_SIZEOF:
+    case AST_OFFSETOF:
         return ast_type_unsigned_long;
     case AST_CAST:
     case AST_VA_ARG:

frontends/c/cgram.y

@@ -1134,6 +1134,7 @@ ConstructDefaultValue(AST *decl, AST *val)
 %token C_BUILTIN_COGSTART "__builtin_cogstart"
 %token C_BUILTIN_COGSTART_COG "__builtin_cogstart_cog"
 %token C_BUILTIN_EXPECT "__builtin_expect"
+%token C_BUILTIN_OFFSETOF "__builtin_offsetof"
 %token C_BUILTIN_PRINTF "__builtin_printf"
 %token C_BUILTIN_REV    "__builtin_rev"
 %token C_BUILTIN_VA_START "__builtin_va_start"
@@ -1414,7 +1415,9 @@ unary_expression
 	| C_SIZEOF '(' type_name ')'
             { $$ = NewAST(AST_SIZEOF, $3, NULL); }           
 	| C_SIZEOF unary_expression
-            { $$ = NewAST(AST_SIZEOF, $2, NULL); }           
+            { $$ = NewAST(AST_SIZEOF, $2, NULL); }
+	| C_BUILTIN_OFFSETOF '(' type_name ',' C_IDENTIFIER ')'
+            { $$ = NewAST(AST_OFFSETOF, $3, $5); }
 	;
 
 unary_operator

frontends/hloptimize.c

@@ -241,6 +241,7 @@ doCheckLocalVar(Symbol *sym, AST *body, VarUse identifierUse, AST **where)
         // like memset(foo, 0, sizeof(foo)) work
         return doCheckLocalVar(sym, body->left, VAR_SET, where);
     case AST_SIZEOF:
+    case AST_OFFSETOF:
         /* these expressions do not actually evaluate their parameters */
         return VAR_UNUSED;
     case AST_ASSIGN: