- RtlSetEnvironmentVariable: To delete a variable, it is necessary to pass a NULL pointer as the value; passing an empty string should create an empty variable. Remove Value->Length > 0 check.

- SetEnvironmentVariable(A|W): When given a NULL value, pass NULL to RtlSetEnvironmentVariable.
- cmd_set: When given an empty value, pass NULL to SetEnvironmentVariable.

svn path=/trunk/; revision=35672

reactos/base/shell/cmd/set.c

@@ -154,7 +154,7 @@ INT cmd_set (LPTSTR param)
 		}
 
 		*p++ = _T('\0');
-		if (!SetEnvironmentVariable(param, p))
+		if (!SetEnvironmentVariable(param, *p ? p : NULL))
 		{
 			nErrorLevel = 1;
 			return 1;

reactos/dll/win32/kernel32/misc/env.c

@@ -193,6 +193,8 @@ SetEnvironmentVariableA (
 	                              &VarName,
 	                              TRUE);
 
+	if (lpValue)
+	{
 		RtlInitAnsiString (&VarValue,
 		                   (LPSTR)lpValue);
 		RtlAnsiStringToUnicodeString (&VarValueU,
@@ -203,8 +205,15 @@ SetEnvironmentVariableA (
 		                                    &VarNameU,
 		                                    &VarValueU);
 
-	RtlFreeUnicodeString (&VarNameU);
 		RtlFreeUnicodeString (&VarValueU);
+	}
+	else
+	{
+		Status = RtlSetEnvironmentVariable (NULL,
+		                                    &VarNameU,
+		                                    NULL);
+	}
+	RtlFreeUnicodeString (&VarNameU);
 
 	if (!NT_SUCCESS(Status))
 	{
@@ -235,12 +244,22 @@ SetEnvironmentVariableW (
 	RtlInitUnicodeString (&VarName,
 	                      lpName);
 
+	if (lpValue)
+	{
 		RtlInitUnicodeString (&VarValue,
 		                      lpValue);
 
 		Status = RtlSetEnvironmentVariable (NULL,
 		                                    &VarName,
 		                                    &VarValue);
+	}
+	else
+	{
+		Status = RtlSetEnvironmentVariable (NULL,
+		                                    &VarName,
+		                                    NULL);
+	}
+
 	if (!NT_SUCCESS(Status))
 	{
 		SetLastErrorByStatus (Status);

reactos/lib/rtl/env.c

@@ -355,7 +355,7 @@ RtlSetEnvironmentVariable(PWSTR *Environment,
    }
 
 found:
-   if (Value != NULL && Value->Length > 0)
+   if (Value != NULL)
    {
       hole_len = tail - hole;
       /* calculate new environment size */