[Tarantool-patches] [PATCH luajit] Fix os.date() for wider libc strftime() compatibility.

[Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

From: Mike Pall <mike>

Thanks to Jesper Lundgren.

(cherry picked from commit fc63c938b522e147ea728b75f385728bf4a8fc35)

When `strftime()` returns empty result (for example, for "%p" on some
locales or when LuaJIT is built with musl's `strftime()` and format
string is invalid), the `os.date()` endless retries to format result
and reallocates buffer for resulting string. This leads to OOM.

This patch limits amount of retries by 4.

Sergey Kaplun:
* added the description and the test for the problem

Part of tarantool/tarantool#8069
---

PR: https://github.com/tarantool/tarantool/pull/8237
Issues:
* https://github.com/LuaJIT/LuaJIT/issues/463
* https://github.com/tarantool/tarantool/issues/8069
Branch: https://github.com/tarantool/luajit/tree/skaplun/lj-463-os-date-oom-full-ci

 src/lib_os.c                                  |  4 ++--
 .../lj-463-os-date-oom.test.lua               | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 test/tarantool-tests/lj-463-os-date-oom.test.lua

diff --git a/src/lib_os.c b/src/lib_os.c
index 9e78d49a..ffbc3fdc 100644
--- a/src/lib_os.c
+++ b/src/lib_os.c
@@ -205,12 +205,12 @@ LJLIB_CF(os_date)
     setboolfield(L, "isdst", stm->tm_isdst);
   } else if (*s) {
     SBuf *sb = &G(L)->tmpbuf;
-    MSize sz = 0;
+    MSize sz = 0, retry = 4;
     const char *q;
     for (q = s; *q; q++)
       sz += (*q == '%') ? 30 : 1;  /* Overflow doesn't matter. */
     setsbufL(sb, L);
-    for (;;) {
+    while (retry--) {  /* Limit growth for invalid format or empty result. */
       char *buf = lj_buf_need(sb, sz);
       size_t len = strftime(buf, sbufsz(sb), s, stm);
       if (len) {
diff --git a/test/tarantool-tests/lj-463-os-date-oom.test.lua b/test/tarantool-tests/lj-463-os-date-oom.test.lua
new file mode 100644
index 00000000..cce78b6e
--- /dev/null
+++ b/test/tarantool-tests/lj-463-os-date-oom.test.lua
@@ -0,0 +1,19 @@
+local tap = require('tap')
+
+-- See also https://github.com/LuaJIT/LuaJIT/issues/463.
+local test = tap.test('lj-463-os-date-oom')
+test:plan(1)
+
+-- The ru_RU.utf8 locale is chosen as one that will be set on a
+-- developer's PC with high possibility. It may be unavailable at
+-- CI, so don't check the status and result of function calls.
+-- If it's unavailable `os.setlocale()` does nothing.
+-- Before the patch, the call to `os.date('%p')` on non-standard
+-- locale may lead to OOM.
+
+os.setlocale('ru_RU.utf8')
+os.date('%p')
+
+test:ok(true, 'os.date() finished without OOM')
+
+os.exit(test:check() and 0 or 1)
-- 
2.34.1