From d81861ed01ffb50ab9f0b5ceab3f4df70510d531 Mon Sep 17 00:00:00 2001 From: Zack Weinberg Date: Sat, 28 Nov 2020 10:01:31 -0500 Subject: =?UTF-8?q?AC=5FFUNC=5FSETPGRP:=20Don=E2=80=99t=20depend=20on=20th?= =?UTF-8?q?e=20return=20type=20of=20setpgrp.?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit AC_FUNC_SETPGRP determines whether you have the historic BSD setpgrp, which takes two arguments and returns int, or the historic POSIX setpgrp, which takes no arguments and returns int. Solaris has yet a third variant, which takes no arguments and returns a pid_t (the new process group ID). This difference causes AC_FUNC_SETPGRP’s test program to fail to compile under AC_LANG([C++]), which in turn causes the macro to report that setpgrp does take arguments, which is wrong. It is not worth adding a new result #define for this variant, since *all* forms of setpgrp are deprecated in favor of setpgid, which is old enough that it can be used unconditionally. However, it is worth documenting that this variant exists, and fixing AC_FUNC_SETPGRP to produce the right value for its existing result #define on Solaris with C++. * lib/autoconf/functions.m4 (AC_FUNC_SETPGRP): Redesign test program to not depend on the return type of setpgrp. * doc/autoconf.texi (AC_FUNC_SETPGRP): Mention that the macro does not check for the Solaris variant of setpgrp that returns pid_t. Change programming advice to recommend use of setpgid. --- doc/autoconf.texi | 10 +++++++--- lib/autoconf/functions.m4 | 17 ++++++++--------- 2 files changed, 15 insertions(+), 12 deletions(-) diff --git a/doc/autoconf.texi b/doc/autoconf.texi index e8abc9ff..9ba182af 100644 --- a/doc/autoconf.texi +++ b/doc/autoconf.texi @@ -5599,13 +5599,17 @@ If @code{setpgrp} takes no argument (the Posix version), define @code{SETPGRP_VOID}. Otherwise, it is the BSD version, which takes two process IDs as arguments. This macro does not check whether @code{setpgrp} exists at all; if you need to work in that situation, -first call @code{AC_CHECK_FUNC} for @code{setpgrp}. +first call @code{AC_CHECK_FUNC} for @code{setpgrp}. This macro also +does not check for the Solaris variant of @code{setpgrp}, which returns +a @code{pid_t} instead of an @code{int}; portable code should only use +the return value by comparing it against @code{-1} to check for errors. The result of this macro is cached in the @code{ac_cv_func_setpgrp_void} variable. -This macro is obsolescent, as current systems have a @code{setpgrp} -whose signature conforms to Posix. New programs need not use this macro. +This macro is obsolescent, as all forms of @code{setpgrp} are also +obsolescent. New programs should use the Posix function @code{setpgid}, +which takes two process IDs as arguments (like the BSD @code{setpgrp}). @end defmac @defmac AC_FUNC_STAT diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4 index a91eeebc..49aa5c58 100644 --- a/lib/autoconf/functions.m4 +++ b/lib/autoconf/functions.m4 @@ -1541,17 +1541,16 @@ rm -rf conftest* # AC_FUNC_SETPGRP # --------------- AC_DEFUN([AC_FUNC_SETPGRP], -[AC_CACHE_CHECK(whether setpgrp takes no argument, ac_cv_func_setpgrp_void, - [AC_COMPILE_IFELSE( - [AC_LANG_PROGRAM( - [[#include - static int (*p) (void) = setpgrp;]], - [[return setpgrp ();]])], - [ac_cv_func_setpgrp_void=yes], - [ac_cv_func_setpgrp_void=no])]) +[AC_CACHE_CHECK(whether setpgrp requires zero arguments, + ac_cv_func_setpgrp_void, +[# Call it with two arguments. +AC_COMPILE_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT], [setpgrp(0, 0);])], + [ac_cv_func_setpgrp_void=no], + [ac_cv_func_setpgrp_void=yes]) +]) if test $ac_cv_func_setpgrp_void = yes; then AC_DEFINE(SETPGRP_VOID, 1, - [Define to 1 if the `setpgrp' function takes no argument.]) + [Define to 1 if the `setpgrp' function requires zero arguments.]) fi ])# AC_FUNC_SETPGRP -- cgit v1.2.1