Change default open mode to -rw-r--r-- (#2530)

src/os.cc

@@ -32,10 +32,15 @@
 #    ifndef S_IRUSR
 #      define S_IRUSR _S_IREAD
 #    endif
-
 #    ifndef S_IWUSR
 #      define S_IWUSR _S_IWRITE
 #    endif
+#    ifndef S_IRGRP
+#      define S_IRGRP 0
+#    endif
+#    ifndef S_IROTH
+#      define S_IROTH 0
+#    endif
 
 #    ifdef __MINGW32__
 #      define _SH_DENYNO 0x40
@@ -213,7 +218,7 @@ int buffered_file::fileno() const {
 
 #if FMT_USE_FCNTL
 file::file(cstring_view path, int oflag) {
-  int mode = S_IRUSR | S_IWUSR;
+  int mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
 #  if defined(_WIN32) && !defined(__MINGW32__)
   fd_ = -1;
   FMT_POSIX_CALL(sopen_s(&fd_, path.c_str(), oflag, _SH_DENYNO, mode));