https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79956
--- Comment #27 from rguenther at suse dot de <rguenther at suse dot de> --- On Sun, 12 Mar 2017, tkoenig at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79956 > > --- Comment #24 from Thomas Koenig <tkoenig at gcc dot gnu.org> --- > I think the warning about estat is a gcc bug. > > Here is the function in its entirety: > > void > execute_command_line_i4 (const char *command, GFC_LOGICAL_4 *wait, > GFC_INTEGER_4 *exitstat, GFC_INTEGER_4 *cmdstat, > char *cmdmsg, gfc_charlen_type command_len, > gfc_charlen_type cmdmsg_len) > { > bool w = wait ? *wait : true; > int estat, estat_initial, cstat; > > if (exitstat) > estat_initial = estat = *exitstat; > > execute_command_line (command, w, &estat, cmdstat ? &cstat : NULL, > cmdmsg, command_len, cmdmsg_len); > > if (exitstat && estat != estat_initial) > *exitstat = estat; > if (cmdstat) > *cmdstat = cstat; > } > > estat gets a value if exitstat is non-NULL. There is nothing > in the code that could legally change the value of exitstat, > and the value of estat is only used on the condition that > exitstat is non-NULL. You are right. I've seen a few other cases where odd jump-threading managed to isolate an obviously dead path through the CFG which is enough to confuse the warning. > If anything, second test is unnecessary, and this could be > shortened to > > if (exitstat) > estat_initial = estat = *exitstat; > > execute_command_line (command, w, &estat, cmdstat ? &cstat : NULL, > cmdmsg, command_len, cmdmsg_len); > > if (exitstat) > *exitstat = estat; > > Does this fix the warning, by any chance? This would be quite > elegant :-) Indeed - looking at the code you wonder what that estat_initial is about -- it's just extra state that needs to be kept alive across the execute_command_line function call to avoid writing to *exitstat.
