minizip: place erase temp on same filesystem when TMPDIR differs

minizip_erase rewrites the archive to a temp file under TMPDIR and
then renames it onto the source. rename(2) returns EXDEV across
filesystems, so when TMPDIR (e.g. /tmp) and the source live on
different mounts (a common conda-forge pattern), the rename fails
after the original was already moved aside to .bak — the next
operation that opens the archive sees no file and reports -111.

Add mz_os_path_same_fs() and have minizip_erase fall back on POSIX to
a same-dir temp when TMPDIR is on a different filesystem. POSIX uses
stat() st_dev comparison; Win32 uses _wstati64 for the parallel check
but the caller skips it under #ifndef _WIN32 because MoveFileExW with
MOVEFILE_COPY_ALLOWED already absorbs cross-volume rename internally.

Make the same-dir tmp filename unique (mz_ms_time suffix) and refuse
to clobber an existing leftover from a prior crash.

Refs #943.

minizip.c

@@ -444,6 +444,28 @@ int32_t minizip_erase(const char *src_path, const char *target_path, int32_t arg
         /* Construct temporary zip name with random suffix */
         if (mz_os_get_temp_path(tmp_path, sizeof(tmp_path), "mz_") != MZ_OK)
             return MZ_INTERNAL_ERROR;
+
+#ifndef _WIN32
+        /* POSIX rename(2) returns EXDEV across mounts; fall back to a same-dir tmp when
+           TMPDIR is on a different filesystem. MoveFileExW absorbs cross-volume natively
+           on Win32, so the check is skipped there. */
+        {
+            char tmp_dir[256];
+
+            strncpy(tmp_dir, tmp_path, sizeof(tmp_dir) - 1);
+            tmp_dir[sizeof(tmp_dir) - 1] = 0;
+            mz_path_remove_filename(tmp_dir);
+
+            if (mz_os_path_same_fs(tmp_dir, src_path) != MZ_OK) {
+                int32_t result = snprintf(tmp_path, sizeof(tmp_path), "%s.mz_tmp.%llu", src_path,
+                                          (unsigned long long)mz_os_ms_time());
+                if (result < 0 || result >= (int32_t)sizeof(tmp_path))
+                    return MZ_BUF_ERROR;
+                if (mz_os_file_exists(tmp_path) == MZ_OK)
+                    return MZ_EXIST_ERROR;
+            }
+        }
+#endif
         target_path_ptr = tmp_path;
     }
 

mz_os.h

@@ -154,6 +154,9 @@ int32_t mz_os_set_file_attribs(const char *path, uint32_t attributes);
 int32_t mz_os_get_temp_path(char *path, int32_t max_path, const char *prefix);
 /* Gets a unique temporary file path */
 
+int32_t mz_os_path_same_fs(const char *path_a, const char *path_b);
+/* Checks if both paths are on the same filesystem */
+
 int32_t mz_os_make_dir(const char *path);
 /* Recursively creates a directory */
 

mz_os_posix.c

@@ -165,6 +165,15 @@ int32_t mz_os_rename(const char *source_path, const char *target_path) {
     return MZ_OK;
 }
 
+int32_t mz_os_path_same_fs(const char *path_a, const char *path_b) {
+    struct stat sa, sb;
+    if (!path_a || !path_b)
+        return MZ_PARAM_ERROR;
+    if (stat(path_a, &sa) != 0 || stat(path_b, &sb) != 0)
+        return MZ_EXIST_ERROR;
+    return (sa.st_dev == sb.st_dev) ? MZ_OK : MZ_EXIST_ERROR;
+}
+
 int32_t mz_os_unlink(const char *path) {
     if (unlink(path) == -1)
         return MZ_EXIST_ERROR;

mz_os_win32.c

@@ -12,6 +12,9 @@
 #include "mz_os.h"
 #include "mz_strm_os.h"
 
+#include <sys/types.h>
+#include <sys/stat.h>
+
 #include <windows.h>
 #include <winioctl.h>
 
@@ -114,6 +117,35 @@ int32_t mz_os_rand(uint8_t *buf, int32_t size) {
     return len;
 }
 
+int32_t mz_os_path_same_fs(const char *path_a, const char *path_b) {
+    wchar_t *path_a_wide = NULL;
+    wchar_t *path_b_wide = NULL;
+    struct _stati64 sa;
+    struct _stati64 sb;
+    int32_t err = MZ_OK;
+
+    if (!path_a || !path_b)
+        return MZ_PARAM_ERROR;
+
+    path_a_wide = mz_os_unicode_string_create(path_a, MZ_ENCODING_UTF8);
+    if (!path_a_wide)
+        return MZ_PARAM_ERROR;
+    path_b_wide = mz_os_unicode_string_create(path_b, MZ_ENCODING_UTF8);
+    if (!path_b_wide) {
+        mz_os_unicode_string_delete(&path_a_wide);
+        return MZ_PARAM_ERROR;
+    }
+
+    if (_wstati64(path_a_wide, &sa) != 0 || _wstati64(path_b_wide, &sb) != 0)
+        err = MZ_EXIST_ERROR;
+    else if (sa.st_dev != sb.st_dev)
+        err = MZ_EXIST_ERROR;
+
+    mz_os_unicode_string_delete(&path_a_wide);
+    mz_os_unicode_string_delete(&path_b_wide);
+    return err;
+}
+
 int32_t mz_os_rename(const char *source_path, const char *target_path) {
     wchar_t *source_path_wide = NULL;
     wchar_t *target_path_wide = NULL;