* generic/tclExecute.c (NEXT_INST_F):

	* generic/tclInt.h (TCL_CT_ASSERT): new compile-time assertions,
	adapted from www.pixelbeat.org/programming/gcc/static_assert.html

2 files changed, 44 insertions, 40 deletions

diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index ba7bd62..fd79931 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -14,7 +14,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclExecute.c,v 1.411 2008/09/10 13:24:12 msofer Exp $
+ * RCS: @(#) $Id: tclExecute.c,v 1.412 2008/09/18 15:43:15 msofer Exp $
  */
 
 #include "tclInt.h"
@@ -257,35 +257,37 @@ VarHashCreateVar(
  *    resultHandling: 0 indicates no object should be pushed on the stack;
  *	otherwise, push objResultPtr. If (result < 0), objResultPtr already
  *	has the correct reference count.
+ *
+ * We use the new compile-time assertions to cheack that nCleanup is constant
+ * and within range.
  */
 
 #define NEXT_INST_F(pcAdjustment, nCleanup, resultHandling) \
-    if (nCleanup == 0) {\
-	if (resultHandling != 0) {\
-	    if ((resultHandling) > 0) {\
-		PUSH_OBJECT(objResultPtr);\
-	    } else {\
-		*(++tosPtr) = objResultPtr;\
-	    }\
-	} \
-	pc += (pcAdjustment);\
-	goto cleanup0;\
-    } else if (resultHandling != 0) {\
-	if ((resultHandling) > 0) {\
-	    Tcl_IncrRefCount(objResultPtr);\
-	}\
-	pc += (pcAdjustment);\
-	switch (nCleanup) {\
-	    case 1: goto cleanup1_pushObjResultPtr;\
-	    case 2: goto cleanup2_pushObjResultPtr;\
-	    default: Tcl_Panic("bad usage of macro NEXT_INST_F");\
+    TCL_CT_ASSERT((nCleanup >= 0) && (nCleanup <= 2));	    \
+    if (nCleanup == 0) {				    \
+	if (resultHandling != 0) {			    \
+	    if ((resultHandling) > 0) {			    \
+		PUSH_OBJECT(objResultPtr);		    \
+	    } else {					    \
+		*(++tosPtr) = objResultPtr;		    \
+	    }						    \
+	}						    \
+	pc += (pcAdjustment);				    \
+	goto cleanup0;					    \
+    } else if (resultHandling != 0) {			    \
+	if ((resultHandling) > 0) {			    \
+	    Tcl_IncrRefCount(objResultPtr);		    \
+	}						    \
+	pc += (pcAdjustment);				    \
+	switch (nCleanup) {				    \
+	    case 1: goto cleanup1_pushObjResultPtr;	    \
+	    case 2: goto cleanup2_pushObjResultPtr;	    \
 	}\
     } else {\
 	pc += (pcAdjustment);\
 	switch (nCleanup) {\
 	    case 1: goto cleanup1;\
 	    case 2: goto cleanup2;\
-	    default: Tcl_Panic("bad usage of macro NEXT_INST_F");\
 	}\
     }
 
@@ -2399,7 +2401,7 @@ TclExecuteByteCode(
 	    TclNewObj(newObjResultPtr);
 	    Tcl_IncrRefCount(newObjResultPtr);
 	    iPtr->objResultPtr = newObjResultPtr;
-	    NEXT_INST_V(opnd, 0, -1);
+	    NEXT_INST_F(opnd, 0, -1);
 	}
 
     case INST_DUP:
diff --git a/generic/tclInt.h b/generic/tclInt.h
index 10deb4c..d13efb4 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -15,7 +15,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclInt.h,v 1.397 2008/09/17 18:11:32 dgp Exp $
+ * RCS: @(#) $Id: tclInt.h,v 1.398 2008/09/18 15:43:21 msofer Exp $
  */
 
 #ifndef _TCLINT
@@ -4035,13 +4035,27 @@ MODULE_SCOPE void	TclBNInitBignumFromWideUInt(mp_int *bignum,
 	    ? 1 : 0)))
 
 /*
+ * Compile-time assertions: these produce a compile time error if
+ * the expression is not known to be true at compile time.
+ * If the assertion is known to be false, the compiler (or optimizer?) will
+ * error out with "division by zero". If the assertion cannot be evaluated at
+ * compile time, the compiler will error out with "non-static initializer".
+ *
+ * Adapted with permission from
+ * http://www.pixelbeat.org/programming/gcc/static_assert.html
+ */
+
+#define TCL_ASSERT_CONCAT_(a, b) a##b
+#define TCL_ASSERT_CONCAT(a, b) TCL_ASSERT_CONCAT_(a, b)
+#define TCL_CT_ASSERT(e) \
+    {enum { TCL_ASSERT_CONCAT(tclCtAssert_, __LINE__) = 1/(!!(e)) };}
+
+/*
  *----------------------------------------------------------------
  * Allocator for small structs (<=sizeof(Tcl_Obj)) using the Tcl_Obj pool.
  * Only checked at compile time.
  *
- * ONLY USE FOR CONSTANT nBytes: if you do and nBytes is too large, the
- * compiler will error out with "duplicate case value" (thanks dkf!). If the
- * size is dynamic, a panic will be compiled in for the wrong case.
+ * ONLY USE FOR CONSTANT nBytes.
  *
  * DO NOT LET THEM CROSS THREAD BOUNDARIES
  *----------------------------------------------------------------
@@ -4057,13 +4071,7 @@ MODULE_SCOPE void	TclBNInitBignumFromWideUInt(mp_int *bignum,
 #define TclSmallAllocEx(interp, nbytes, memPtr)				\
     {									\
 	Tcl_Obj *objPtr;						\
-	switch ((nbytes)>sizeof(Tcl_Obj)) {				\
-	    case (2 +((nbytes)>sizeof(Tcl_Obj))):			\
-	    case 3:							\
-	    case 1:							\
-		Tcl_Panic("TclSmallAlloc: nBytes too large!");		\
-	    case 0: (void)0;						\
-	}								\
+	TCL_CT_ASSERT((nbytes)<=sizeof(Tcl_Obj));			\
 	TclIncrObjsAllocated();						\
 	TclAllocObjStorageEx((interp), (objPtr));			\
 	memPtr = (ClientData) (objPtr);					\
@@ -4077,13 +4085,7 @@ MODULE_SCOPE void	TclBNInitBignumFromWideUInt(mp_int *bignum,
 #define TclSmallAllocEx(interp, nbytes, memPtr)				\
     {									\
 	Tcl_Obj *objPtr;						\
-	switch ((nbytes)>sizeof(Tcl_Obj)) {				\
-	    case (2 +((nbytes)>sizeof(Tcl_Obj))):			\
-	    case 3:							\
-	    case 1:							\
-		Tcl_Panic("TclSmallAlloc: nBytes too large!");		\
-	    case 0: (void)0;						\
-	}								\
+	TCL_CT_ASSERT((nbytes)<=sizeof(Tcl_Obj));			\
 	TclNewObj(objPtr);						\
 	memPtr = (ClientData) objPtr;					\
     }