1 files changed, 9 insertions, 6 deletions

diff --git a/src/lisp.h b/src/lisp.h
index 3795795c49a..21f652b81ac 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4496,12 +4496,15 @@ enum MAX_ALLOCA { MAX_ALLOCA = 16 * 1024 };
 extern void *record_xmalloc (size_t) ATTRIBUTE_ALLOC_SIZE ((1));
 
 #define USE_SAFE_ALLOCA                 \
+  ptrdiff_t sa_avail = MAX_ALLOCA;      \
   ptrdiff_t sa_count = SPECPDL_INDEX (); bool sa_must_free = false
 
+#define AVAIL_ALLOCA(size) (sa_avail -= (size), alloca (size))
+
 /* SAFE_ALLOCA allocates a simple buffer.  */
 
-#define SAFE_ALLOCA(size) ((size) <= MAX_ALLOCA \
-                           ? alloca (size)      \
+#define SAFE_ALLOCA(size) ((size) <= sa_avail                           \
+                           ? AVAIL_ALLOCA (size)                        \
                            : (sa_must_free = true, record_xmalloc (size)))
 
 /* SAFE_NALLOCA sets BUF to a newly allocated array of MULTIPLIER *
@@ -4510,8 +4513,8 @@ extern void *record_xmalloc (size_t) ATTRIBUTE_ALLOC_SIZE ((1));
 
 #define SAFE_NALLOCA(buf, multiplier, nitems)                    \
   do {                                                           \
-    if ((nitems) <= MAX_ALLOCA / sizeof *(buf) / (multiplier))   \
-      (buf) = alloca (sizeof *(buf) * (multiplier) * (nitems));  \
+    if ((nitems) <= sa_avail / sizeof *(buf) / (multiplier))     \
+      (buf) = AVAIL_ALLOCA (sizeof *(buf) * (multiplier) * (nitems)); \
     else                                                         \
       {                                                          \
         (buf) = xnmalloc (nitems, sizeof *(buf) * (multiplier)); \
@@ -4543,8 +4546,8 @@ extern void *record_xmalloc (size_t) ATTRIBUTE_ALLOC_SIZE ((1));
 
 #define SAFE_ALLOCA_LISP(buf, nelt)                            \
   do {                                                         \
-    if ((nelt) <= MAX_ALLOCA / word_size)                      \
-      (buf) = alloca ((nelt) * word_size);                     \
+    if ((nelt) <= sa_avail / word_size)                        \
+      (buf) = AVAIL_ALLOCA ((nelt) * word_size);               \
     else if ((nelt) <= min (PTRDIFF_MAX, SIZE_MAX) / word_size) \
       {                                                        \
         Lisp_Object arg_;                                      \