From 9b5699737a6b587546239d586832f420cf7f2dea Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Fri, 9 Jul 2021 10:22:40 +1000
Subject: detect struct stat.st_dev's size and signedness, and return it safely

On FreeBSD dev_t (and hence the st_dev member of struct stat) is an
unsigned 64-bit integer, and the previous simple PUSHi() corrupted
that.

A previous version of this reflected the st_ino code and implemented
our own number to string conversion, but a system with such a large
st_dev should be assumed to have inttypes.h, and an intmax_t which is
no smaller than st_dev.

The st_ino code could probably be changed similarly, but 64-bit inode
numbers are not a new thing, so it may be riskier.
---
 pp_sys.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

(limited to 'pp_sys.c')

diff --git a/pp_sys.c b/pp_sys.c
index 9b2d64ae2e..cb449c3d9e 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -2916,7 +2916,38 @@ PP(pp_stat)
     if (max) {
         EXTEND(SP, max);
         EXTEND_MORTAL(max);
+#if ST_DEV_SIZE < IVSIZE || (ST_DEV_SIZE == IVSIZE && ST_DEV_SIGN < 0)
         mPUSHi(PL_statcache.st_dev);
+#elif ST_DEV_SIZE == IVSIZE
+        mPUSHu(PL_statcache.st_dev);
+#else
+#  if ST_DEV_SIGN < 0
+        if (LIKELY((IV)PL_statcache.st_dev == PL_statcache.st_dev)) {
+            mPUSHi((IV)PL_statcache.st_dev);
+        }
+#  else
+        if (LIKELY((UV)PL_statcache.st_dev == PL_statcache.st_dev)) {
+            mPUSHu((UV)PL_statcache.st_dev);
+        }
+#  endif
+        else {
+            char buf[sizeof(PL_statcache.st_dev)*3+1];
+            /* sv_catpvf() casts 'j' size values down to IV, so it
+               isn't suitable for use here.
+            */
+#    if defined(I_INTTYPES) && defined(HAS_SNPRINTF)
+#      if ST_DEV_SIGN < 0
+            int size = snprintf(buf, sizeof(buf), "%" PRIdMAX, (intmax_t)PL_statcache.st_dev);
+#      else
+            int size = snprintf(buf, sizeof(buf), "%" PRIuMAX, (uintmax_t)PL_statcache.st_dev);
+#      endif
+            STATIC_ASSERT_STMT(sizeof(intmax_t) >= sizeof(PL_statcache.st_dev));
+            mPUSHp(buf, size);
+#    else
+#      error extraordinarily large st_dev but no inttypes.h or no snprintf
+#    endif
+        }
+#endif
         {
             /*
              * We try to represent st_ino as a native IV or UV where
-- 
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