From patchwork Tue Dec 6 16:43:27 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Zack Weinberg X-Patchwork-Id: 18239 Received: (qmail 33248 invoked by alias); 6 Dec 2016 16:43:41 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 33176 invoked by uid 89); 6 Dec 2016 16:43:41 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.4 required=5.0 tests=AWL, BAYES_00, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, RCVD_IN_SORBS_SPAM, SPF_PASS autolearn=no version=3.3.2 spammy=Unlike, standardization, occurred X-HELO: mail-qt0-f194.google.com X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to; bh=wlOGMdbiwh0tOII4E9WXmpB5UtzbJ9g1wJP2ff2BrQg=; b=kUNNI0zA+wA/TD1n2EoMYVwh82Bo7JJZu9F21ZROsBAA4iEhPv/u7wSfRSI7axsSF4 YEmSzGKmmYObqoPSEWJ/VT15dUDEpuDpnqMM0C8aLToDrslnTW/VkylWMHkm9qOpIXUw ruOvQmdOZn0CH6WpN1nH2gbEO9ESQkh52eb+WETqFhOs5VvzL/6ORIB5W7BYHpTozqi2 xYjTFChnwDQNkSy93n3zeATTIpK0qURiWobg3gMZSVME78WegapLJJoAgv9mtodBTggy zxdjaG/BAsMX6opIDWtL80C//sNATZEoxeYVdf7sGrSF3/AMqwY1OHqVYu+TjtSWZjkw ByFw== X-Gm-Message-State: AKaTC00Wcx8cZanI8O67GpxpRPK2ugelR8QiyPgykwpQ5TFKopUJuD/3tYC9z5rFrscD1A== X-Received: by 10.237.36.90 with SMTP id s26mr56003113qtc.114.1481042608709; Tue, 06 Dec 2016 08:43:28 -0800 (PST) Subject: Re: [RFC PATCH] Deprecate _REENTRANT and _THREAD_SAFE. To: libc-alpha@sourceware.org References: <20161206152204.2064-1-zackw@panix.com> <8e3a2e59-8275-d188-6a7e-54d92cbd1417@redhat.com> From: Zack Weinberg Message-ID: <611abaa8-6ffe-50b9-d369-46f8161b2529@panix.com> Date: Tue, 6 Dec 2016 11:43:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.5.1 MIME-Version: 1.0 In-Reply-To: <8e3a2e59-8275-d188-6a7e-54d92cbd1417@redhat.com> On 12/06/2016 10:36 AM, Florian Weimer wrote: > On 12/06/2016 04:22 PM, Zack Weinberg wrote: >> For many years, the only effect of these macros has been to make >> unistd.h declare getlogin_r. _POSIX_C_SOURCE >= 199506L also causes >> this function to be declared. However, people who don't carefully >> read all the headers might be confused into thinking they need to >> define _REENTRANT for any threaded code (as was indeed the case a long >> time ago). > > You should get rid of the internal #define and #undef of _REENTRANT, too. Do you mean the ones in libc-symbols.h and check-installed-headers.sh? Those are the only ones I see grepping. This updated patch takes care of that and also the discussion in creature.texi. (creature.texi needs a thorough overhaul, but let's not worry about that now.) Also, it's been tested on x86-64-linux. zw From 8e04a5fe9858410311c71da92cfa119e2710213a Mon Sep 17 00:00:00 2001 From: Zack Weinberg Date: Tue, 6 Dec 2016 10:14:42 -0500 Subject: [PATCH] Deprecate _REENTRANT and _THREAD_SAFE. For many years, the only effect of these macros has been to make unistd.h declare getlogin_r. _POSIX_C_SOURCE >= 199506L also causes this function to be declared. However, people who don't carefully read all the headers might be confused into thinking they need to define _REENTRANT for any threaded code (as was indeed the case a long time ago). Therefore, I propose to make _REENTRANT and _THREAD_SAFE into aliases for _POSIX_C_SOURCE=199506L, and issue a deprecation warning when a higher conformance level was not selected some other way. For instance, -std=c89 -D_REENTRANT will warn, but -std=c99 -D_POSIX_C_SOURCE=200809L -D_REENTRANT won't, and -D_REENTRANT all by itself also won't, because _DEFAULT_SOURCE implies _POSIX_C_SOURCE > 199506. I could be persuaded to make that final case also warn. * NEWS: The feature selection macros _REENTRANT and _THREAD_SAFE are deprecated. * manual/creature.texi: Document them as obsolete. * include/features.h: Treat them as synonyms for _POSIX_C_SOURCE=199506L, if a higher POSIX conformance level has not been selected by other macros. * posix/unistd.h, posix/bits/unistd.h: Don't check __USE_REENTRANT. * include/libc-symbols.h: Don't define _REENTRANT. * scripts/check-installed-headers.sh: Don't undefine _REENTRANT. --- NEWS | 10 ++++++++++ include/features.h | 39 ++++++++++++++++++++++++-------------- include/libc-symbols.h | 2 -- manual/creature.texi | 12 ++++-------- posix/bits/unistd.h | 2 +- posix/unistd.h | 2 +- scripts/check-installed-headers.sh | 1 - 7 files changed, 41 insertions(+), 27 deletions(-) diff --git a/NEWS b/NEWS index c2e973d..4f72149 100644 --- a/NEWS +++ b/NEWS @@ -22,6 +22,16 @@ Version 2.25 from that TS. Note that most features from that TS are not supported by the GNU C Library. +* The feature test macros _REENTRANT and _THREAD_SAFE are deprecated, and + will henceforth be treated as synonyms for _POSIX_C_SOURCE=199506L. + For many years, their only effect has been to cause to declare + getlogin_r; _POSIX_C_SOURCE=199506L has the same effect. Since the + GNU C Library defaults to a much newer revision of POSIX, this will + only affect programs that specifically request an old conformance mode. + (For instance, a program compiled with -std=c89 -D_REENTRANT will see a + change in the visible declarations, but a program compiled with + -std=c99 -D_POSIX_C_SOURCE=200809L -D_REENTRANT will not.) + * The inclusion of by is deprecated. This means that in a future release, the macros “major”, “minor”, and “makedev” will only be available from . diff --git a/include/features.h b/include/features.h index 650d4c5..5de950c 100644 --- a/include/features.h +++ b/include/features.h @@ -24,10 +24,13 @@ __STRICT_ANSI__ ISO Standard C. _ISOC99_SOURCE Extensions to ISO C89 from ISO C99. _ISOC11_SOURCE Extensions to ISO C99 from ISO C11. - __STDC_WANT_LIB_EXT2__ Extensions to ISO C99 from TR 27431-2:2010. - __STDC_WANT_IEC_60559_BFP_EXT__ Extensions to ISO C11 from TS 18661-1:2014. - __STDC_WANT_IEC_60559_FUNCS_EXT__ Extensions to ISO C11 from - TS 18661-4:2015. + __STDC_WANT_LIB_EXT2__ + Extensions to ISO C99 from TR 27431-2:2010. + __STDC_WANT_IEC_60559_BFP_EXT__ + Extensions to ISO C11 from TS 18661-1:2014. + __STDC_WANT_IEC_60559_FUNCS_EXT__ + Extensions to ISO C11 from TS 18661-4:2015. + _POSIX_SOURCE IEEE Std 1003.1. _POSIX_C_SOURCE If ==1, like _POSIX_SOURCE; if >=2 add IEEE Std 1003.2; if >=199309L, add IEEE Std 1003.1b-1993; @@ -45,10 +48,12 @@ _GNU_SOURCE All of the above, plus GNU extensions. _DEFAULT_SOURCE The default set of features (taking precedence over __STRICT_ANSI__). - _REENTRANT Select additionally reentrant object. - _THREAD_SAFE Same as _REENTRANT, often used by other systems. - _FORTIFY_SOURCE If set to numeric value > 0 additional security - measures are defined, according to level. + + _FORTIFY_SOURCE Add security hardening to many library functions. + Set to 1 or 2; 2 performs stricter checks than 1. + + _REENTRANT, _THREAD_SAFE + Obsolete; equivalent to _POSIX_C_SOURCE=199506L. The `-ansi' switch to the GNU C compiler, and standards conformance options such as `-std=c99', define __STRICT_ANSI__. If none of @@ -86,7 +91,6 @@ __USE_MISC Define things from 4.3BSD or System V Unix. __USE_ATFILE Define *at interfaces and AT_* constants for them. __USE_GNU Define GNU extensions. - __USE_REENTRANT Define reentrant/thread-safe *_r functions. __USE_FORTIFY_LEVEL Additional security measures used, according to level. The macros `__GNU_LIBRARY__', `__GLIBC__', and `__GLIBC_MINOR__' are @@ -130,7 +134,6 @@ #undef __USE_MISC #undef __USE_ATFILE #undef __USE_GNU -#undef __USE_REENTRANT #undef __USE_FORTIFY_LEVEL #undef __KERNEL_STRICT_NAMES @@ -253,6 +256,7 @@ # undef _POSIX_C_SOURCE # define _POSIX_C_SOURCE 200809L #endif + #if ((!defined __STRICT_ANSI__ \ || (defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) >= 500)) \ && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE) @@ -269,6 +273,17 @@ # define __USE_POSIX_IMPLICITLY 1 #endif +/* _REENTRANT and _THREAD_SAFE are obsolete aliases for _POSIX_C_SOURCE=199506L. + Only issue a warning if _POSIX_C_SOURCE was not already defined to + an equivalent or higher level some other way. */ +#if ((!defined _POSIX_C_SOURCE || (_POSIX_C_SOURCE - 0) < 199506L) \ + && (defined _REENTRANT || defined _THREAD_SAFE)) +# warning "_REENTRANT and _THREAD_SAFE are deprecated, use _POSIX_C_SOURCE" +# define _POSIX_SOURCE 1 +# undef _POSIX_C_SOURCE +# define _POSIX_C_SOURCE 199506L +#endif + #if (defined _POSIX_SOURCE \ || (defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 1) \ || defined _XOPEN_SOURCE) @@ -351,10 +366,6 @@ # define __USE_GNU 1 #endif -#if defined _REENTRANT || defined _THREAD_SAFE -# define __USE_REENTRANT 1 -#endif - #if defined _FORTIFY_SOURCE && _FORTIFY_SOURCE > 0 # if !defined __OPTIMIZE__ || __OPTIMIZE__ <= 0 # warning _FORTIFY_SOURCE requires compiling with optimization (-O) diff --git a/include/libc-symbols.h b/include/libc-symbols.h index 1c91f2e..4238d79 100644 --- a/include/libc-symbols.h +++ b/include/libc-symbols.h @@ -52,8 +52,6 @@ /* Enable declarations of GNU extensions, since we are compiling them. */ #define _GNU_SOURCE 1 -/* And we also need the data for the reentrant functions. */ -#define _REENTRANT 1 #include diff --git a/manual/creature.texi b/manual/creature.texi index 257f871..5048886 100644 --- a/manual/creature.texi +++ b/manual/creature.texi @@ -219,15 +219,11 @@ cause them to be disabled. @comment GNU @defvr Macro _REENTRANT @defvrx Macro _THREAD_SAFE -If you define one of these macros, reentrant versions of several functions get -declared. Some of the functions are specified in POSIX.1c but many others -are only available on a few other systems or are unique to @theglibc{}. -The problem is the delay in the standardization of the thread safe C library -interface. +These macros are obsolete. They have the same effect as defining +@code{_POSIX_C_SOURCE} with the value @code{199506L}. -Unlike on some other systems, no special version of the C library must be -used for linking. There is only one version but while compiling this -it must have been specified to compile as thread safe. +Some very old C libraries required one of these macros to be defined +for basic functionality (e.g.@: @code{getchar}) to be thread-safe. @end defvr We recommend you use @code{_GNU_SOURCE} in new programs. If you don't diff --git a/posix/bits/unistd.h b/posix/bits/unistd.h index 0105f04..4a5f42e 100644 --- a/posix/bits/unistd.h +++ b/posix/bits/unistd.h @@ -302,7 +302,7 @@ __NTH (ttyname_r (int __fd, char *__buf, size_t __buflen)) } -#if defined __USE_REENTRANT || defined __USE_POSIX199506 +#ifdef __USE_POSIX199506 extern int __getlogin_r_chk (char *__buf, size_t __buflen, size_t __nreal) __nonnull ((1)); extern int __REDIRECT (__getlogin_r_alias, (char *__buf, size_t __buflen), diff --git a/posix/unistd.h b/posix/unistd.h index 625ba77..392dc0e 100644 --- a/posix/unistd.h +++ b/posix/unistd.h @@ -849,7 +849,7 @@ extern int tcsetpgrp (int __fd, __pid_t __pgrp_id) __THROW; This function is a possible cancellation point and therefore not marked with __THROW. */ extern char *getlogin (void); -#if defined __USE_REENTRANT || defined __USE_POSIX199506 +#ifdef __USE_POSIX199506 /* Return at most NAME_LEN characters of the login name of the user in NAME. If it cannot be determined or some other error occurred, return the error code. Otherwise return 0. diff --git a/scripts/check-installed-headers.sh b/scripts/check-installed-headers.sh index a245fe6..89e1514 100644 --- a/scripts/check-installed-headers.sh +++ b/scripts/check-installed-headers.sh @@ -143,7 +143,6 @@ EOF inappropriate for this test. */ #undef _LIBC #undef _GNU_SOURCE -#undef _REENTRANT /* The library mode is selected here rather than on the command line to ensure that this selection wins. */ $expanded_lib_mode -- 2.10.2