Hi, Ramsay Jones wrote: > In particular, some versions of gcc complains as follows: > > CC vcs-svn/sliding_window.o > vcs-svn/sliding_window.c: In function `check_overflow': > vcs-svn/sliding_window.c:36: warning: comparison is always false \ > due to limited range of data type Yuck. Suppressing this warning would presumably also suppress the optimization that notices the comparison is always false. The -Wtype-limits warning also triggers in some other perfectly reasonable situations: see <http://gcc.gnu.org/PR51712>. I wonder if we should keep a list of unreliable warnings somewhere (e.g., Meta/Make). [...] > Note that the "some versions of gcc" which complain includes 3.4.4 and > 4.1.2, whereas gcc version 4.4.0 compiles the code without complaint. Thanks for tracking this down. Interesting. -Wtype-limits was split out from the default set of warnings (!) in gcc 4.3 to address <http://gcc.gnu.org/PR12963>, among other bugs (r124875, 2007-05-20). [...] > --- a/vcs-svn/fast_export.c > +++ b/vcs-svn/fast_export.c > @@ -300,7 +300,8 @@ void fast_export_blob_delta(uint32_t mode, > uint32_t len, struct line_buffer *input) > { > long postimage_len; > - if (len > maximum_signed_value_of_type(off_t)) > + uintmax_t delta_len = (uintmax_t) len; > + if (delta_len > maximum_signed_value_of_type(off_t)) > die("enormous delta"); > postimage_len = apply_delta((off_t) len, input, old_data, old_mode); Is there some less ugly way to write the condition "if this value is not representable in this type"? I guess I could live with something like the following (please don't take the names too seriously): static inline off_t off_t_or_die(uintmax_t val, const char *msg_if_bad) { if (val > maximum_signed_value_of_type(off_t)) die("%s", msg_if_bad); return (off_t) val; } ... off_t delta_len = off_t_or_die(len, "enormous delta"); postimage_len = apply_delta(delta_len, input, ...); What do you think? Jonathan -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html