From aa64597e8ba0e4a2da32a0a351c43aa27eb8e165 Mon Sep 17 00:00:00 2001
From: Leonid Yuriev <leo@yuriev.ru>
Date: Sat, 13 Oct 2018 12:47:12 +0300
Subject: [PATCH] mdbx: avoid on-stack allocation/chkstk inside
 mdbx_env_walk().

5 of 17 for https://github.com/leo-yuriev/libmdbx/issues/43

Change-Id: Iadb833ff38dbd0922eda69238b365f5906b9109f
---
 src/mdbx.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/mdbx.c b/src/mdbx.c
index 243aae22..d1ad912c 100644
--- a/src/mdbx.c
+++ b/src/mdbx.c
@@ -12793,9 +12793,20 @@ static int __cold mdbx_env_walk(mdbx_walk_ctx_t *ctx, const char *dbi,
 
       MDBX_db db;
       memcpy(&db, NODEDATA(node), sizeof(db));
-      char *name = memcpy(alloca(namelen + 1), NODEKEY(node), namelen);
-      name[namelen] = 0;
-      rc = mdbx_env_walk(ctx, name, db.md_root, deep + 1);
+
+      char namebuf_onstask[142];
+      char *const name = (namelen < sizeof(namebuf_onstask))
+                             ? namebuf_onstask
+                             : mdbx_malloc(namelen + 1);
+      if (name) {
+        memcpy(name, NODEKEY(node), namelen);
+        name[namelen] = 0;
+        rc = mdbx_env_walk(ctx, name, db.md_root, deep + 1);
+        if (name != namebuf_onstask)
+          mdbx_free(name);
+      } else {
+        rc = MDBX_ENOMEM;
+      }
     } break;
 
     case F_SUBDATA | F_DUPDATA /* dupsorted sub-tree */: {