From 7a85168daf6036fee808dac9944161415189f8a4 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Mon, 6 Apr 2015 12:35:18 +0100 Subject: 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), we trip 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: #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. Work around that by simply using __attribute__((weak)). Windows/PE/COFF's do support weak, but not on gcc 3.4 based toolchains (4.8.x does work). Given the file never needed the variables while it was Windows-only, just continue not defining them there. All other supported hosts should support this. gdb/ChangeLog: 2015-04-06 Pedro Alves Bernd Edlinger * 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 [!__MINGW32__] (PC, BC, UP): Define as weak symbols. --- gdb/stub-termcap.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) (limited to 'gdb/stub-termcap.c') diff --git a/gdb/stub-termcap.c b/gdb/stub-termcap.c index 5897d89..722929f 100644 --- a/gdb/stub-termcap.c +++ b/gdb/stub-termcap.c @@ -40,9 +40,28 @@ extern char *tgoto (const char *cap, int col, int row); } #endif +/* These globals below 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. + Don't do this on Windows though, as MinGW gcc 3.4.2 doesn't support + weak (later versions, e.g., 4.8, do support it). Given this stub + file originally was Windows only, and we only needed this when we + made it work on other hosts, it should be OK. */ +#ifndef __MINGW32__ +char PC __attribute__((weak)); +char *BC __attribute__((weak)); +char *UP __attribute__((weak)); +#endif + /* 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) -- cgit v1.1