zsh @5.8: wrong configure results because of implicit function declarations

[joelburton (Joel Burton)]

tart zsh without rcs (this should start a new shell):

/usr/local/bin/zsh --no-rcs

try to enter the following in the new shell (it should hang):

echo $(date)

To me it seems like all command substitution using $() causes zsh to hang. Backticks seem to work though.

(Copying report from ​https://github.com/Homebrew/discussions/discussions/141 ; this is about a problem with Homebrew, but I'm getting the same behavior with MacPorts0.

[ryandesign (Ryan Carsten Schmidt)]

If you see the same problem with zsh regardless whether zsh is installed with MacPorts or Homebrew, that suggests a bug in zsh that should be reported to the developers of zsh. You could also check whether you get the same problem with /bin/zsh as provided by Apple, but even if you don't, that doesn't mean it's not a zsh bug; Apple probably modifies their zsh just as they modify all of the software they ship with macOS.

[ryandesign (Ryan Carsten Schmidt)]

Per ​the fix that Homebrew committed, it was a problem with implicit function declarations: a common problem we are seeing with many, many ports under Xcode 12. Whereas Homebrew chose to downgrade the error to a warning, the correct fix is to include the right headers so that the function declarations are provided. Not doing so can spell trouble for Apple Silicon systems.

[ryandesign (Ryan Carsten Schmidt)]

$ grep \ implicit -r work/zsh-5.8/config.log
work/zsh-5.8/config.log:conftest.c:225:14: error: implicit declaration of function 'tgetent' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:230:6: error: implicit declaration of function 'tgetstr' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:231:2: error: implicit declaration of function 'creat' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:233:5: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:225:14: error: implicit declaration of function 'tgetent' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:230:6: error: implicit declaration of function 'tgetstr' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:231:2: error: implicit declaration of function 'creat' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:233:5: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:251:24: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:251:40: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:283:5: error: implicit declaration of function 'unlink' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:285:8: error: implicit declaration of function 'mkfifo' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:289:2: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:290:11: error: implicit declaration of function 'fork' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:295:17: error: implicit declaration of function 'read' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:298:22: error: implicit declaration of function 'write' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:287:2: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:283:5: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:298:9: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:282:5: error: implicitly declaring library function 'sprintf' with type 'int (char *, const char *, ...)' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:282:27: error: implicit declaration of function 'getpid' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:282:37: error: implicit declaration of function 'rand' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:284:14: error: implicitly declaring library function 'strcpy' with type 'char *(char *, const char *)' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:287:5: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:287:31: error: implicitly declaring library function 'strcmp' with type 'int (const char *, const char *)' [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:293:5: error: implicit declaration of function 'read' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
work/zsh-5.8/config.log:conftest.c:315:13: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]

[larryv (Lawrence Velázquez)]

adaptation of upstream's fix