From patchwork Thu Feb 26 17:48:06 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pedro Alves X-Patchwork-Id: 5318 Received: (qmail 27828 invoked by alias); 26 Feb 2015 17:48:25 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 27809 invoked by uid 89); 26 Feb 2015 17:48:23 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL, BAYES_00, SPF_HELO_PASS, SPF_PASS, T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Thu, 26 Feb 2015 17:48:21 +0000 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t1QHm9QF015633 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 26 Feb 2015 12:48:09 -0500 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t1QHm73B026190; Thu, 26 Feb 2015 12:48:07 -0500 Message-ID: <54EF5C56.9010101@redhat.com> Date: Thu, 26 Feb 2015 17:48:06 +0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Bernd Edlinger CC: GDB Patches , Doug Evans , Mike Frysinger Subject: Re: [PATCH] Enable building GDB without installed libtermcap References: <54EB4FDF.1060909@redhat.com>, <54EB513A.8050706@redhat.com> In-Reply-To: On 02/24/2015 06:13 PM, Bernd Edlinger wrote: > Ok, thanks for this hint! > > That is probably exactly what I need. > > This makes the patch much smaller. > > Maybe the name windows-termcap.c is a bit misleading, > because my target is mostly some embedded linux. > (meanwhile the file has been renamed to stub-termcap.c) > How about this: > --- a/gdb/configure.ac > +++ b/gdb/configure.ac > @@ -621,7 +621,7 @@ esac > AC_SEARCH_LIBS(tgetent, [termcap tinfo curses ncurses]) > > if test "$ac_cv_search_tgetent" = no; then > - AC_MSG_ERROR([no termcap library found]) > + CONFIG_OBS="$CONFIG_OBS windows-termcap.o" > fi Yes, but I think we should remove the mingw specific fallback a bit above too. > > AC_ARG_WITH([system-readline], > diff --git a/gdb/windows-termcap.c b/gdb/windows-termcap.c > index caafc47..b6e0d08 100644 > --- a/gdb/windows-termcap.c > +++ b/gdb/windows-termcap.c > @@ -32,6 +32,8 @@ extern char* tgetstr (char *name, char **area); > extern int tputs (char *string, int nlines, int (*outfun) ()); > extern char *tgoto (const char *cap, int col, int row); > > +char PC, *BC, *UP; > + I was doing what I suggest above, and tripped on the need for this too, without realizing you had this here already. GDB is converting to C++ (and people build with -fno-common too, e.g., https://sourceware.org/ml/gdb-patches/2015-02/msg00364.html), and there's a problem with just defining these symbols unconditionally here. See patch below for details, and let me know what you (all) think. ---- [PATCH] Fallback to stub-termcap.c on all hosts Currently building gdb is impossible without an installed termcap or curses library. But, GDB already has a very minimal termcap in the tree to handle this situation for Windows -- gdb/stub-termcap.c. This patch makes that the fallback for all hosts. Testing this on GNU/Linux (by simply hacking away the termcap/curses detection in gdb/configure.ac), I tripped on: ../readline/libreadline.a(terminal.o): In function `_rl_init_terminal_io': /home/pedro/gdb/mygit/src/readline/terminal.c:527: undefined reference to `PC' /home/pedro/gdb/mygit/src/readline/terminal.c:528: undefined reference to `BC' /home/pedro/gdb/mygit/src/readline/terminal.c:529: undefined reference to `UP' /home/pedro/gdb/mygit/src/readline/terminal.c:538: undefined reference to `PC' /home/pedro/gdb/mygit/src/readline/terminal.c:539: undefined reference to `BC' /home/pedro/gdb/mygit/src/readline/terminal.c:540: undefined reference to `UP' These are globals that are normally defined by termcap (or ncurses' termcap emulation). Now, we could just define replacements in stub-termcap.c, but readline/terminal.c (at least the copy in our tree) has this "beauty": #if !defined (__linux__) && !defined (NCURSES_VERSION) # if defined (__EMX__) || defined (NEED_EXTERN_PC) extern # endif /* __EMX__ || NEED_EXTERN_PC */ char PC, *BC, *UP; #endif /* !__linux__ && !NCURSES_VERSION */ which can result in readline defining the globals too. That will usually work out in C, given that "-fcommon" is usually the default for C compilers, but that won't work for C++, or C with -fno-common (link fails with "multiple definition" errors)... Mirroring those #ifdef conditions in the stub termcap screams "brittle" to me -- I can see them changing in latter readline versions. My idea to work around that is to simply use __attribute__((weak)). Of all supported hosts (https://sourceware.org/gdb/wiki/Systems#Supported_Hosts), Windows/PE/COFF would be the one that I'd be worried about WRT use of weak, but the limited weak support in PE/COFF seems to work here. A cross build using x86_64-w64-mingw32 on Fedora 20 builds fine with this. gdb/ChangeLog: 2015-02-26 Bernd Edlinger Pedro Alves * configure.ac: Remove the mingw32-specific stub-termcap.o fallback, and instead fallback to the stub termcap on all hosts. * configure: Regenerate. * stub-termcap.c (PC, BC, UP): Define as weak symbols. --- gdb/configure.ac | 7 +------ gdb/stub-termcap.c | 13 ++++++++++++- 2 files changed, 13 insertions(+), 7 deletions(-) diff --git a/gdb/configure.ac b/gdb/configure.ac index 6ac8adb..79fc115 100644 --- a/gdb/configure.ac +++ b/gdb/configure.ac @@ -610,18 +610,13 @@ case $host_os in go32* | *djgpp*) ac_cv_search_tgetent="none required" ;; - *mingw32*) - if test x"$curses_found" != xyes; then - ac_cv_search_tgetent="none required" - CONFIG_OBS="$CONFIG_OBS stub-termcap.o" - fi ;; esac # These are the libraries checked by Readline. AC_SEARCH_LIBS(tgetent, [termcap tinfo curses ncurses]) if test "$ac_cv_search_tgetent" = no; then - AC_MSG_ERROR([no termcap library found]) + CONFIG_OBS="$CONFIG_OBS stub-termcap.o" fi AC_ARG_WITH([system-readline], diff --git a/gdb/stub-termcap.c b/gdb/stub-termcap.c index cc8632c..8704695 100644 --- a/gdb/stub-termcap.c +++ b/gdb/stub-termcap.c @@ -32,9 +32,20 @@ extern char* tgetstr (char *name, char **area); extern int tputs (char *string, int nlines, int (*outfun) ()); extern char *tgoto (const char *cap, int col, int row); +/* These are global termcap variables that readline references. + Actually, depending on preprocessor conditions that we don't want + to mirror here (as they may change depending on readline versions), + readline may define these globals as well, relying on the linker + merging them if needed (-fcommon). That doesn't work with + -fno-common or C++, so instead we define the symbols as weak. */ +char PC __attribute__((weak)); +char *BC __attribute__((weak)); +char *UP __attribute__((weak)); + /* Each of the files below is a minimal implementation of the standard termcap function with the same name, suitable for use in a Windows - console window. */ + console window, or when a real termcap/curses library isn't + available. */ int tgetent (char *buffer, char *termtype)