From e50eb17003bcced57d4ed139bba042694988350e Mon Sep 17 00:00:00 2001
From: Greg Haerr <greg@censoft.com>
Date: Fri, 13 Dec 2024 20:06:47 -0700
Subject: [PATCH] [libc] Further fixes to v7malloc

---
 libc/malloc/v7malloc.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/libc/malloc/v7malloc.c b/libc/malloc/v7malloc.c
index 1256a6840..4e13548c6 100644
--- a/libc/malloc/v7malloc.c
+++ b/libc/malloc/v7malloc.c
@@ -102,12 +102,13 @@ malloc(size_t nbytes)
     if (nbytes < MINALLOC)
         nbytes = MINALLOC;
 
-    /* check INT overflow beyond 32764 (nbytes/WORD+WORD+(WORD-1) > 0xFFFF/WORD/WORD)*/
-    if (nbytes > ((unsigned)-1)/WORD-WORD-(WORD-1)) {
+    /* check INT overflow beyond 32762 (nbytes/WORD+WORD+WORD+(WORD-1) > 0xFFFF/WORD/WORD)*/
+    if (nbytes > ((unsigned)-1)/WORD-WORD-WORD-(WORD-1)) {
         debug(" (req too big) = NULL\n");
         errno = ENOMEM;
         return(NULL);
     }
+
     nw = (nbytes+WORD+WORD-1)/WORD;          /* extra word for link ptr/size*/
 
     ASSERT(allocp>=allocs && allocp<=alloct);
@@ -118,12 +119,15 @@ allocp = (union store __wcnear *)allocs;    /* experimental */
         for(temp=0; ; ) {
             if(!testbusy(p->ptr)) {
                 while(!testbusy((q=p->ptr)->ptr)) {
+                    if (debug_level > 2) malloc_show_heap();
                     ASSERT(q>p);
                     ASSERT(q<alloct);
                     debug("(combine %u and %u) ",
                         (char *)p->ptr - (char *)p, (char *)q->ptr - (char *)q);
                     p->ptr = q->ptr;
                 }
+                debug2("q %04x p %04x nw %d p+nw %04x ", (unsigned)q, (unsigned)p,
+                    nw, (unsigned)(p+nw));
                 if(q>=p+nw && p+nw>=p)
                     goto found;
             }
@@ -140,17 +144,19 @@ allocp = (union store __wcnear *)allocs;    /* experimental */
                 break;
         }
 
-        /* extend break at least BLOCK bytes at a time*/
+        /* extend break at least BLOCK bytes at a time, plus a word for top link */
         if (nw < BLOCK/WORD)
-            temp = BLOCK/WORD;
+            temp = BLOCK/WORD + 1;
         else
-            temp = nw;
+            temp = nw + 1; /* NOTE always allocates full req w/o looking at free at top */
 
+        if (debug_level > 2) malloc_show_heap();
         debug("sbrk(%d) ", temp*WORD);
-        /* ensure next sbrk returns even address*/
+#if 0   /* not required and slow, initial break always even */
         q = (union store __wcnear *)sbrk(0);
         if((INT)q & (sizeof(union store) - 1))
             sbrk(4 - ((INT)q & (sizeof(union store) - 1)));
+#endif
 
         /* check possible address wrap*/
         if(q+temp+GRANULE < q) {