[219226]: Rewrote how ::env is synchronized to the environment so it no longer

smashes the array or its elements flat, This affects traces on env, links to
env, and iterations over env: it makes them work as naïvely expected.

4 files changed, 137 insertions, 16 deletions

diff --git a/generic/tclEnv.c b/generic/tclEnv.c
index b5ae6ea..6a21947 100644
--- a/generic/tclEnv.c
+++ b/generic/tclEnv.c
@@ -76,36 +76,56 @@ TclSetupEnv(
     Tcl_Interp *interp)		/* Interpreter whose "env" array is to be
 				 * managed. */
 {
+    Var *varPtr, *arrayPtr;
+    Tcl_Obj *varNamePtr;
     Tcl_DString envString;
-    char *p1, *p2;
-    int i;
+    Tcl_HashTable namesHash;
+    Tcl_HashEntry *hPtr;
+    Tcl_HashSearch search;
 
     /*
      * Synchronize the values in the environ array with the contents of the
      * Tcl "env" variable. To do this:
-     *    1) Remove the trace that fires when the "env" var is unset.
-     *    2) Unset the "env" variable.
-     *    3) If there are no environ variables, create an empty "env" array.
-     *	     Otherwise populate the array with current values.
-     *    4) Add a trace that synchronizes the "env" array.
+     *    1) Remove the trace that fires when the "env" var is updated.
+     *    2) Find the existing contents of the "env", storing in a hash table.
+     *    3) Create/update elements for each environ variable, removing
+     *	     elements from the hash table as we go.
+     *    4) Remove the elements for each remaining entry in the hash table,
+     *	     which must have existed before yet have no analog in the environ
+     *	     variable.
+     *    5) Add a trace that synchronizes the "env" array.
      */
 
     Tcl_UntraceVar2(interp, "env", NULL,
 	    TCL_GLOBAL_ONLY | TCL_TRACE_WRITES | TCL_TRACE_UNSETS |
 	    TCL_TRACE_READS | TCL_TRACE_ARRAY, EnvTraceProc, NULL);
 
-    Tcl_UnsetVar2(interp, "env", NULL, TCL_GLOBAL_ONLY);
+    /*
+     * Find out what elements are currently in the global env array.
+     */
 
-    if (environ[0] == NULL) {
-	Tcl_Obj *varNamePtr;
+    TclNewLiteralStringObj(varNamePtr, "env");
+    Tcl_IncrRefCount(varNamePtr);
+    Tcl_InitObjHashTable(&namesHash);
+    varPtr = TclObjLookupVarEx(interp, varNamePtr, NULL, TCL_GLOBAL_ONLY,
+	    /*msg*/ 0, /*createPart1*/ 0, /*createPart2*/ 0, &arrayPtr);
+    TclFindArrayPtrElements(varPtr, &namesHash);
+
+    /*
+     * Go through the environment array and transfer its values into Tcl. At
+     * the same time, remove those elements we add/update from the hash table
+     * of existing elements, so that after this part processes, that table
+     * will hold just the parts to remove.
+     */
+
+    if (environ[0] != NULL) {
+	int i;
 
-	TclNewLiteralStringObj(varNamePtr, "env");
-	Tcl_IncrRefCount(varNamePtr);
-	TclArraySet(interp, varNamePtr, NULL);
-	Tcl_DecrRefCount(varNamePtr);
-    } else {
 	Tcl_MutexLock(&envMutex);
 	for (i = 0; environ[i] != NULL; i++) {
+	    Tcl_Obj *obj1, *obj2;
+	    char *p1, *p2;
+
 	    p1 = Tcl_ExternalToUtfDString(NULL, environ[i], -1, &envString);
 	    p2 = strchr(p1, '=');
 	    if (p2 == NULL) {
@@ -119,12 +139,41 @@ TclSetupEnv(
 	    }
 	    p2++;
 	    p2[-1] = '\0';
-	    Tcl_SetVar2(interp, "env", p1, p2, TCL_GLOBAL_ONLY);
+	    obj1 = Tcl_NewStringObj(p1, -1);
+	    obj2 = Tcl_NewStringObj(p2, -1);
 	    Tcl_DStringFree(&envString);
+
+	    Tcl_IncrRefCount(obj1);
+	    Tcl_IncrRefCount(obj2);
+	    Tcl_ObjSetVar2(interp, varNamePtr, obj1, obj2, TCL_GLOBAL_ONLY);
+	    hPtr = Tcl_FindHashEntry(&namesHash, obj1);
+	    if (hPtr != NULL) {
+		Tcl_DeleteHashEntry(hPtr);
+	    }
+	    Tcl_DecrRefCount(obj1);
+	    Tcl_DecrRefCount(obj2);
 	}
 	Tcl_MutexUnlock(&envMutex);
     }
 
+    /*
+     * Delete those elements that existed in the array but which had no
+     * counterparts in the environment array.
+     */
+
+    for (hPtr=Tcl_FirstHashEntry(&namesHash, &search); hPtr!=NULL;
+	    hPtr=Tcl_NextHashEntry(&search)) {
+	Tcl_Obj *elemName = Tcl_GetHashValue(hPtr);
+
+	TclObjUnsetVar2(interp, varNamePtr, elemName, TCL_GLOBAL_ONLY);
+    }
+    Tcl_DeleteHashTable(&namesHash);
+    Tcl_DecrRefCount(varNamePtr);
+
+    /*
+     * Re-establish the trace.
+     */
+
     Tcl_TraceVar2(interp, "env", NULL,
 	    TCL_GLOBAL_ONLY | TCL_TRACE_WRITES | TCL_TRACE_UNSETS |
 	    TCL_TRACE_READS | TCL_TRACE_ARRAY, EnvTraceProc, NULL);
diff --git a/generic/tclInt.h b/generic/tclInt.h
index 380284f..feea6dd 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -3857,6 +3857,8 @@ MODULE_SCOPE int	TclPtrUnsetVar(Tcl_Interp *interp, Var *varPtr,
 			    Tcl_Obj *part2Ptr, const int flags,
 			    int index);
 MODULE_SCOPE void	TclInvalidateNsPath(Namespace *nsPtr);
+MODULE_SCOPE void	TclFindArrayPtrElements(Var *arrayPtr,
+			    Tcl_HashTable *tablePtr);
 
 /*
  * The new extended interface to the variable traces.
diff --git a/generic/tclVar.c b/generic/tclVar.c
index af1a563..4694cd8 100644
--- a/generic/tclVar.c
+++ b/generic/tclVar.c
@@ -3850,6 +3850,53 @@ ArrayNamesCmd(
 /*
  *----------------------------------------------------------------------
  *
+ * TclFindArrayPtrElements --
+ *
+ *	Fill out a hash table (which *must* use Tcl_Obj* keys) with an entry
+ *	for each existing element of the given array. The provided hash table
+ *	is assumed to be initially empty.
+ *
+ * Result:
+ *	none
+ *
+ * Side effects:
+ *	The keys of the array gain an extra reference. The supplied hash table
+ *	has elements added to it.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+TclFindArrayPtrElements(
+    Var *arrayPtr,
+    Tcl_HashTable *tablePtr)
+{
+    Var *varPtr;
+    Tcl_HashSearch search;
+
+    if ((arrayPtr == NULL) || !TclIsVarArray(arrayPtr)
+	    || TclIsVarUndefined(arrayPtr)) {
+	return;
+    }
+
+    for (varPtr=VarHashFirstVar(arrayPtr->value.tablePtr, &search);
+	    varPtr!=NULL ; varPtr=VarHashNextVar(&search)) {
+	Tcl_HashEntry *hPtr;
+	Tcl_Obj *nameObj;
+	int dummy;
+
+	if (TclIsVarUndefined(varPtr)) {
+	    continue;
+	}
+	nameObj = VarHashGetKey(varPtr);
+	hPtr = Tcl_CreateHashEntry(tablePtr, (char *) nameObj, &dummy);
+	Tcl_SetHashValue(hPtr, nameObj);
+    }
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * ArraySetCmd --
  *
  *	This object-based function is invoked to process the "array set" Tcl
diff --git a/tests/env.test b/tests/env.test
index fa76433..8115652 100644
--- a/tests/env.test
+++ b/tests/env.test
@@ -291,6 +291,29 @@ test env-6.1 {corner cases - add lots of env variables} {} {
     expr {[array size env] - $size}
 } 100
 
+test env-7.1 {[219226]: whole env array should not be unset by read} {
+    set n [array size env]
+    set s [array startsearch env]
+    while {[array anymore env $s]} {
+	array nextelement env $s
+	incr n -1
+    }
+    array donesearch env $s
+    return $n
+} 0
+test env-7.2 {[219226]: links to env elements should not be removed by read} {
+    apply {{} {
+	set ::env(test7_2) ok
+	upvar env(test7_2) elem
+	set ::env(PATH)
+	try {
+	    return $elem
+	} finally {
+	    unset ::env(test7_2)
+	}
+    }}
+} ok
+
 # Restore the environment variables at the end of the test.
 
 foreach name [array names env] {