Testing whether the compiler supports it is a bit tricky.
The obvious AX_APPEND_COMPILE_FLAGS([-fstack-protector-strong])
doesn't suffice, since some ports of the GNU toolchain reportedly pass
this test, then fail to link. That's because the compiler accepts the
flag, duly emits references to helper code in libc, but libc doesn't
provide, and linking fails.
Instead, use AX_APPEND_LINK_FLAGS with an input source that makes the
compiler emit the extra stack checking code. This requires the latest
version from the autoconf-archive, so update m4/ax* to commit e3d948b.
Also update m4/my_append_compile_flags.m4 to keep it in sync with
upstream's ax_append_compile_flags.m4.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Contemporary compilers can squeeze out some extra performance by
assuming the program never executes code that has undefined behavior
according to the C standard. Unfortunately, this can break programs.
Pointing out that these programs are non-conforming is as correct as
it is unhelpful, at least as long as the compiler is unable to
diagnose the non-conformingness.
Since keeping our programs working is a lot more important to us than
running them as fast as possible, forbid some assumptions that are
known to break real-world programs:
* Aliasing: perfectly clean programs don't engage in type-punning, and
perfectly conforming programs do it only in full accordance with the
standard's (subtle!) aliasing rules. Neither kind of perfection is
realistic for us, therefore -fno-strict-aliasing.
* Signed integer overflow: perfectly clean programs won't ever do
signed integer arithmetic that overflows. This is an imperfect
program, therefore -fno-strict-overflow.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Renaming carg() would be smarter, but I'd rather do that as part of a
consistent renaming of all command functions, and I'm not up to that
right now.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
When AC_PROG_CC detects GCC, Make.mk adds a bunch of flags to CFLAGS.
Works only for flags that any version of gcc in use accepts.
Instead, make configure add the flags that actually work to CFLAGS.
This will let us add flags that work only for some compilers.
The new autoconf macros are from autoconf-archive v2015.02.24.
Unfortunately, AX_APPEND_COMPILE_FLAGS doesn't work reliably for
-Wno-*: gcc complains about unknown -Wno-foo only when other
diagnostics are being produced. Test -Wfoo instead of -Wno-foo, and
rename to MY_APPEND_COMPILE_FLAGS.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Why upgrade? I'm not a lawyer, but here's my take on the differences
to version 2:
* Software patents: better protection against abuse of patents to
prevent users from exercising the rights under the GPL. I doubt
we'll get hit with a patent suit, but it's a good move just on
general principles.
* License compatibility: compatible with more free licenses, i.e. can
"steal" more free software for use in Empire. I don't expect to steal
much, but it's nice to have the option.
* Definition of "source code": modernization of some details for today's
networked world, to make it easier to distribute the software. Not
really relevant to us now, as we normally distribute full source code.
* Tivoization: this is about putting GPL-licensed software in hardware,
then make the hardware refuse to run modified software. "Neat" trick
to effectively deny its users their rights under the GPL. Abuse was
"pioneered" by TiVo (popular digital video recorders). GPLv3 forbids
it. Unlikely to become a problem for us.
* Internationalization: more careful wording, to harden the license
outside the US. The lawyers tell us it better be done that way.
* License violations: friendlier way to deal with license violations.
This has come out of past experience enforcing the GPL.
* Additional permissions: Probably not relevant to us.
Also include myself in the list of principal authors.
configure checked for library functions with LIBS instead of
LIBS_server, which could break detection of getaddrinfo() on systems
where LIB_SOCKET isn't empty.
GNUmakefile put @PTHREAD_LIBS@ only in LDLIBS, which breaks linking of
server and possibly client on systems where it is not empty.
Broken in commit 8b778634.
Make configure compute three sets of libraries: LIBS_client for the
client, LIBS_server for the server, and LIBS for the rest. This
replaces termlibs.
Unfortunately, LIBS doesn't work with Windows, because
src/lib/w32/posixio.c pulls in socket stuff. Temporary workaround:
use LIBS_server instead.
Checking Windows libraries with autoconf is cumbersome, because
linking often fails unless you include the header, and AC_SEARCH_LIBS
doesn't permit that.
Just detect the Windows API instead, with new MY_WINDOWS_API.
getpass() is traditional Unix, but has been withdrawn from POSIX. As
such, it may be missing. Check for that, and provide ersatz. It's
not a real replacement, because it doesn't do the special magic
getpass() is supposed to do: read from /dev/tty without echo.
This bypasses our existing getpass() for Windows. In contrast to the
portable getpass(), the Windows one tries to turn off echo, but that
doesn't work for me (MinGW & Wine). Remove it.
