From 096def8f55e60953e4bf3353a1720b65660b642b Mon Sep 17 00:00:00 2001
From: "zik.saleeba" <zik.saleeba@21eae674-98b7-11dd-bd71-f92a316d2d60>
Date: Sun, 19 Apr 2009 11:49:01 +0000
Subject: [PATCH] Pointer arithmetic and NULL pointer support added

git-svn-id: http://picoc.googlecode.com/svn/trunk@255 21eae674-98b7-11dd-bd71-f92a316d2d60
---
 TODO                               |  4 ++
 clibrary.c                         | 12 +++++
 expression.c                       | 70 ++++++++++++++++++++----------
 picoc.c                            |  1 +
 picoc.h                            |  2 +
 tests/19_pointer_arithmetic.c      | 20 +++++++++
 tests/19_pointer_arithmetic.expect |  3 ++
 tests/Makefile                     |  3 +-
 8 files changed, 92 insertions(+), 23 deletions(-)
 create mode 100644 tests/19_pointer_arithmetic.c
 create mode 100644 tests/19_pointer_arithmetic.expect

diff --git a/TODO b/TODO
index ccc8aff..caef21d 100644
--- a/TODO
+++ b/TODO
@@ -1,5 +1,9 @@
 TODO
 
+Bugs:
+* assignment in declarators: int *b = &a;
+* #define NORTH  1 ... startnode(NORTH,1,2);
+
 Implement:
 * pointer arithmetic
 * NULL pointers and pointer comparison
diff --git a/clibrary.c b/clibrary.c
index 61b0f64..da98ca6 100644
--- a/clibrary.c
+++ b/clibrary.c
@@ -1,5 +1,8 @@
 #include "picoc.h"
 
+static int TRUEValue = 1;
+static int ZeroValue = 0;
+
 /* initialise a library */
 void LibraryInit(struct Table *GlobalTable, const char *LibraryName, struct LibraryFunction (*FuncList)[])
 {
@@ -22,6 +25,15 @@ void LibraryInit(struct Table *GlobalTable, const char *LibraryName, struct Libr
     }
 }
 
+/* initialise the C library */
+void CLibraryInit()
+{
+    /* define some constants */
+    VariableDefinePlatformVar(NULL, "NULL", &IntType, (union AnyValue *)&ZeroValue, FALSE);
+    VariableDefinePlatformVar(NULL, "TRUE", &IntType, (union AnyValue *)&TRUEValue, FALSE);
+    VariableDefinePlatformVar(NULL, "FALSE", &IntType, (union AnyValue *)&ZeroValue, FALSE);
+}
+
 /* print a string to a stream without using printf/sprintf */
 void PrintStr(const char *Str, CharWriter *PutCh)
 {
diff --git a/expression.c b/expression.c
index 2f8b8a9..e323004 100644
--- a/expression.c
+++ b/expression.c
@@ -150,11 +150,13 @@ void ExpressionStackPushValueNode(struct ParseState *Parser, struct ExpressionSt
 }
 
 /* push a blank value on to the expression stack by type */
-void ExpressionStackPushValueByType(struct ParseState *Parser, struct ExpressionStack **StackTop, struct ValueType *PushType)
+struct Value *ExpressionStackPushValueByType(struct ParseState *Parser, struct ExpressionStack **StackTop, struct ValueType *PushType)
 {
     debugf("ExpressionStackPushValueByType()\n");
     struct Value *ValueLoc = VariableAllocValueFromType(Parser, PushType, FALSE, NULL);
     ExpressionStackPushValueNode(Parser, StackTop, ValueLoc);
+    
+    return ValueLoc;
 }
 
 /* push a value on to the expression stack */
@@ -427,32 +429,56 @@ void ExpressionInfixOperator(struct ParseState *Parser, struct ExpressionStack *
             ExpressionPushFP(Parser, StackTop, ResultFP);
     }
 #endif
-#if 0
-XXX - finish this
-    else if ( (TopValue->Typ->Base == TypePointer && IS_INTEGER_COERCIBLE(BottomValue)) ||
-              (IS_INTEGER_COERCIBLE(TopValue) && BottomValue->Typ->Base == TypePointer) )
+    else if (BottomValue->Typ->Base == TypePointer && IS_INTEGER_COERCIBLE(TopValue))
     {
-        /* pointer infix arithmetic */
-        
-        switch (TopOperatorNode->Op)
+        /* pointer/integer infix arithmetic */
+        int TopInt = COERCE_INTEGER(TopValue);
+        struct PointerValue Pointer;
+        struct Value *StackValue;
+
+        if (Op == TokenEqual || Op == TokenNotEqual)
         {
-            case TokenEqual:                ResultInt = BottomInt == TopInt; ResultIsInt = TRUE; break;
-            case TokenNotEqual:             ResultInt = BottomInt != TopInt; ResultIsInt = TRUE; break;
-            case TokenLessThan:             ResultInt = BottomInt < TopInt; ResultIsInt = TRUE; break;
-            case TokenGreaterThan:          ResultInt = BottomInt > TopInt; ResultIsInt = TRUE; break;
-            case TokenLessEqual:            ResultInt = BottomInt <= TopInt; ResultIsInt = TRUE; break;
-            case TokenGreaterEqual:         ResultInt = BottomInt >= TopInt; ResultIsInt = TRUE; break;
-            case TokenPlus:                 Result = BottomInt + TopInt; break;
-            case TokenMinus:                Result = BottomInt - TopInt; break;
-            default:                        ProgramFail(Parser, "invalid operation"); break;
+            /* comparison to a NULL pointer */
+            if (TopInt != 0) 
+                ProgramFail(Parser, "invalid operation");
+            
+            if (Op == TokenEqual)
+                ExpressionPushInt(Parser, StackTop, BottomValue->Val->Pointer.Segment == NULL);
+            else
+                ExpressionPushInt(Parser, StackTop, BottomValue->Val->Pointer.Segment != NULL);
+        }
+        else if (Op == TokenPlus || Op == TokenMinus)
+        {
+            /* pointer arithmetic */
+            int Size = TypeSize(BottomValue->Typ->FromType, 0);
+            
+            Pointer = BottomValue->Val->Pointer;
+            if (Pointer.Segment == NULL)
+                ProgramFail(Parser, "invalid use of a NULL pointer");
+            
+            if (Op == TokenPlus)
+                Pointer.Offset += TopInt * Size;
+            else
+                Pointer.Offset -= TopInt * Size;
+            
+            /* check pointer bounds */
+            if (Pointer.Offset < 0 || Pointer.Offset > TypeSizeValue(BottomValue->Val->Pointer.Segment) - Size)
+                Pointer.Offset = BottomValue->Val->Pointer.Offset;
+            
+            StackValue = ExpressionStackPushValueByType(Parser, StackTop, BottomValue->Typ);
+            StackValue->Val->Pointer = Pointer;
+        }
+        else if (Op == TokenAssign && TopInt == 0)
+        {
+            /* assign a NULL pointer */
+            if (!BottomValue->IsLValue) 
+                ProgramFail(Parser, "can't assign to this"); 
+            
+            ExpressionStackPushValueByType(Parser, StackTop, BottomValue->Typ);
         }
-        
-        if (ResultIsInt)
-            ExpressionPushInt(Parser, StackTop, ResultInt);
         else
-            ExpressionPushPointer(Parser, StackTop, ResultInt);
+            ProgramFail(Parser, "invalid operation");
     }
-#endif
     else if (Op == TokenAssign)
     {
         /* assign a non-numeric type */
diff --git a/picoc.c b/picoc.c
index e7a84b7..f877454 100644
--- a/picoc.c
+++ b/picoc.c
@@ -9,6 +9,7 @@ void Initialise()
     LexInit();
     TypeInit();
     LibraryInit(&GlobalTable, "c library", &CLibrary);
+    CLibraryInit();
     PlatformLibraryInit();
     LibraryInit(&GlobalTable, "platform library", &PlatformLibrary);
 }
diff --git a/picoc.h b/picoc.h
index 5d0f29b..6cc4688 100644
--- a/picoc.h
+++ b/picoc.h
@@ -241,6 +241,7 @@ extern struct ValueType MacroType;
 extern struct ValueType *CharPtrType;
 extern struct ValueType *CharArrayType;
 extern char *StrEmpty;
+extern struct PointerValue NULLPointer;
 extern struct LibraryFunction CLibrary[];
 extern struct LibraryFunction PlatformLibrary[];
 
@@ -322,6 +323,7 @@ void VariableStringLiteralDefine(char *Ident, struct Value *Val);
 
 /* library.c */
 void LibraryInit(struct Table *GlobalTable, const char *LibraryName, struct LibraryFunction (*FuncList)[]);
+void CLibraryInit();
 void PrintInt(int Num, CharWriter *PutCh);
 void PrintStr(const char *Str, CharWriter *PutCh);
 void PrintFP(double Num, CharWriter *PutCh);
diff --git a/tests/19_pointer_arithmetic.c b/tests/19_pointer_arithmetic.c
new file mode 100644
index 0000000..a85d1e1
--- /dev/null
+++ b/tests/19_pointer_arithmetic.c
@@ -0,0 +1,20 @@
+int a;
+int *b;
+int *c;
+
+a = 42;
+b = &a;
+c = NULL;
+
+printf("%d\n", *b);
+
+if (b == NULL)
+    printf("b is NULL\n");
+else
+    printf("b is not NULL\n");
+
+if (c == NULL)
+    printf("c is NULL\n");
+else
+    printf("c is not NULL\n");
+
diff --git a/tests/19_pointer_arithmetic.expect b/tests/19_pointer_arithmetic.expect
new file mode 100644
index 0000000..0cf781b
--- /dev/null
+++ b/tests/19_pointer_arithmetic.expect
@@ -0,0 +1,3 @@
+42
+b is not NULL
+c is NULL
diff --git a/tests/Makefile b/tests/Makefile
index 2b90d43..6485fe4 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -16,7 +16,8 @@ TESTS=	00_assignment.test \
 	15_recursion.test \
 	16_nesting.test \
 	17_enum.test \
-	18_include.test
+	18_include.test \
+	19_pointer_arithmetic.test
 
 %.test: %.expect %.c
 	@echo Test: $*...