config: delete existing variable before writing new contents

kernel/asmsupt.asm

@@ -327,7 +327,6 @@ strcpy_loop:
 		jmp  short pascal_return
 
 ;******************************************************************                
-%ifndef _INIT                
                 global  FSTRLEN
 FSTRLEN:
                 call pascal_setup
@@ -337,7 +336,6 @@ FSTRLEN:
 		mov   bl,4
 
                 jmp short dostrlen
-%endif
 
 ;**********************************************
                 global  STRLEN

kernel/config.c

@@ -2739,6 +2739,30 @@ VOID DoInstall(void)
   return;
 }
 
+STATIC BYTE far * searchvar(const BYTE * name, int length)
+{
+  BYTE far * pp = master_env;
+  do {
+    if (!fmemcmp(name, pp, length + 1)) {
+      return pp;
+    }
+    pp += fstrlen(pp) + 1;
+  } while (*pp);
+  return NULL;
+}
+
+STATIC void deletevar(const BYTE * name, int length) {
+  int variablelength;
+  BYTE far * pp = searchvar(name, length);
+  if (NULL == pp)
+    return;
+  variablelength = fstrlen(pp) + 1;
+  fmemcpy(pp, pp + variablelength, envp + 3 - (pp + variablelength));
+  /* our fmemcpy always copies forwards */
+  envp -= variablelength;
+  return;
+}
+
 STATIC VOID CmdSet(BYTE *pLine)
 {
   pLine = GetStringArg(pLine, szBuf);
@@ -2747,7 +2771,9 @@ STATIC VOID CmdSet(BYTE *pLine)
   {
     int size;
     strupr(szBuf);        /* all environment variables must be uppercase */
+    size = strlen(szBuf);
     strcat(szBuf, "=");
+    deletevar(szBuf, size);
     pLine = skipwh(++pLine);
     strcat(szBuf, pLine); /* append the variable value (may include spaces) */
     size = strlen(szBuf);

kernel/kernel.ld

@@ -150,6 +150,7 @@ SECTIONS
                 _init_strcpy = INIT_STRCPY;
                 _init_fstrcpy = INIT_FSTRCPY;
                 _init_strlen = INIT_STRLEN;
+                _init_fstrlen = INIT_FSTRLEN;
                 _init_strchr = INIT_STRCHR;
                 _UMB_get_largest = UMB_GET_LARGEST;
 		_init_call_intr = INIT_CALL_INTR;