At Tue, 12 May 2020 17:12:51 -0400, Tom Lane <tgl@sss.pgh.pa.us> wrote in > Alvaro Herrera <alvherre@2ndquadrant.com> writes: > > Fixed one straggler in contrib, and while testing it I realized why > > ccache doesn't pay attention to the changes I was doing in the file: > > ccache compares the *preprocessed* version of the file and only if that > > differs from the version that was cached last, ccache sends the new one > > to the compiler; and of course these comments are not present in the > > preprocessed version, so changing only the comment accomplishes nothing. > > You have to touch one byte outside of any comments. > > Ugh. So the only way ccache could avoid this is to drop the > preprocessed-file comparison check if -Wimplicit-fallthrough is on. > Doesn't really sound like something we'd want to ask them to do. > > > I bet this is going to bite someone ... maybe we'd be better off going > > all the way to -Wimplicit-fallthrough=5 and use the > > __attribute__((fallthrough)) stuff instead. > > I'm not really in favor of the __attribute__ solution --- seems too > gcc-specific. FALLTHROUGH-type comments are understood by other > sorts of tools besides gcc. > > In practice, it doesn't seem like this'll be a huge problem once > we're past the initial fixup stage. We can revisit it later if > that prediction proves wrong, of course.
FWIW, I got a warning for jsonpath_gram.c.
> jsonpath_gram.c:1026:16: warning: this statement may fall through [-Wimplicit-fallthrough=] > if (*++yyp != '\\') > ^ > jsonpath_gram.c:1029:11: note: here > default: > ^~~~~~~
jsonpath_gram.c:1025 > case '\\': > if (*++yyp != '\\') > goto do_not_strip_quotes; > /* Fall through. */ > default:
It is generated code by bison.
$ bison --version bison (GNU Bison) 3.0.4
I just found this just serval minutes ago. Upgrading your bison to the latest
version (3.6) is ok. I'd like we have a better way to share this knowledge through.
I spend ~30 minutes to troubleshooting this issue.