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Use _Noreturn (C11; GNU89) properly

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A function that returns with no value is a different thing from a
function that doesn't return at all.  Those are two orthogonal
concepts, commonly confused.

pthread_create(3) expects a pointer to a start routine that has a
very precise prototype:

    void *(*start_routine)(void *);

However, other thread functions, such as kernel ones, expect:

    void (*start_routine)(void *);

Providing a different one is incorrect, and has only been working
because the ABIs happen to produce a compatible function.

We should use '_Noreturn void', since it's the natural type, and
then provide a '_Noreturn void *' wrapper for pthread functions.

For consistency, replace most cases of __NORETURN or
__attribute__((noreturn)) by _Noreturn.  _Noreturn is understood
by -std=gnu89, so it should be safe to use everywhere.

Ref: https://github.com/openzfs/zfs/pull/13110#discussion_r808450136
Ref: https://software.codidact.com/posts/285972
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Co-authored-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Closes #13120
This commit is contained in:
Alejandro Colomar
2022-03-05 01:25:22 +01:00
committed by GitHub
parent 06b8050678
commit db7f1a91de
30 changed files with 76 additions and 90 deletions
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config/always-compiler-options.m4
-26
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@@ -181,32 +181,6 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_NO_CLOBBERED], [
AC_SUBST([NO_CLOBBERED])
])
dnl #
dnl # Check if cc supports -Wno-cast-function-type option.
dnl #
dnl # We actually invoke it with the --cast-function-type option
dnl # and infer the 'no-' version does or doesn't exist based upon
dnl # the results. This is required because when checking any of
dnl # no- prefixed options gcc always returns success.
dnl #
AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_CC_NO_CAST_FUNCTION_TYPE], [
AC_MSG_CHECKING([whether $CC supports -Wno-cast-function-type])
saved_flags="$CFLAGS"
CFLAGS="$CFLAGS -Werror -Wcast-function-type"
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])], [
NO_CAST_FUNCTION_TYPE=-Wno-cast-function-type
AC_MSG_RESULT([yes])
], [
NO_CAST_FUNCTION_TYPE=
AC_MSG_RESULT([no])
])
CFLAGS="$saved_flags"
AC_SUBST([NO_CAST_FUNCTION_TYPE])
])
dnl #
dnl # Check if cc supports -Wimplicit-fallthrough option.
dnl #