Hi Tom and Peter, On Wed, Sep 2, 2020 at 10:40 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > > Peter Eisentraut <peter.eisentr...@2ndquadrant.com> writes: > > On 2020-09-02 22:43, Jesse Zhang wrote: > >> | conftest.c:184:3: error: implicitly declaring library function > >> 'exit' with type 'void (int) __attribute__((noreturn))' > >> [-Werror,-Wimplicit-function-declaration] > > > Where did the -Werror come from? > > Peter wasn't entirely explicit here, but note the advice at the end of > > https://www.postgresql.org/docs/devel/install-procedure.html > > that you cannot include -Werror in any CFLAGS you tell configure > to use. It'd be nice if autoconf was more robust about that, > but it is not our bug to fix. > > regards, tom lane
If you noticed the full invocation of clang, you'd notice that Werror is nowhere on the command line, even though the error message suggests otherwise. I think this is a behavior from the new AppleClang, here's the minimal repro: int main() { exit(0); } And boom! $ clang -c c.c c.c:1:14: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration] int main() { exit(0); } ^ c.c:1:14: note: include the header <stdlib.h> or explicitly provide a declaration for 'exit' 1 error generated. My environment: $ uname -rsv Darwin 20.0.0 Darwin Kernel Version 20.0.0: Fri Aug 14 00:25:13 PDT 2020; root:xnu-7195.40.44.151.1~4/RELEASE_X86_64 $ clang --version Apple clang version 12.0.0 (clang-1200.0.31.1) Target: x86_64-apple-darwin20.0.0 Thread model: posix InstalledDir: /Library/Developer/CommandLineTools/usr/bin I've heard reports of the same under the latest Xcode 12 on macOS Catalina, but I don't have my hands on such an env. Cheers, Jesse