dim added a comment. In https://reviews.llvm.org/D54724#1303844, @phosek wrote:
> In https://reviews.llvm.org/D54724#1303809, @dim wrote: > > > I think this is the wrong direction, placing "common" code in > > `addCXXStdlibLinkDeps`, which then has all kinds of ugly ifs and switches > > for different OSes? Let different OSes handle this in their own way, maybe. > > > You mean handling this in individual `ToolChain` subclasses? I've considered > doing that. The reason I went with a single method is because we already use > this approach for other types of runtimes like sanitizers, XRay, etc. There'd > be still some duplication for handling different C++ libraries, but I'd be > fine changing the implementation to use that approach if there's a strong > preference for doing so. I think I understand the motivation, it's just that the toolchain classes were split up specifically to avoid `if(OS==foo) ... else if(OS==bar) ... else if(OS==baz)` mazes. So this feels a little like a regression in that sense, putting back the OS-specific ifs in a common function. But I guess it is a pattern that pops up more often. >> Until now I have not encountered an issue where I needed to add -lpthread to >> the link command line for a static C++ application; I think that is only >> needed when you actually use threading primitives? But still, I would >> rather see this in the OS-dependent handling functions. > > Have you been using libc++ or just libstdc++? libstdc++ is cheating a bit, > because it relies on threading functions that are provided by libgcc (which > in turn call into pthread), so -lpthread is not needed when using libstdc++, > even when you link it statically. libc++ doesn't rely on these functions > because it supports different builtin libraries (like compiler-rt) hence > having to specify -lpthread explicitly. We've been using libc++ by default since FreeBSD 10.x, and all older versions are now EOLed. That said, we have always used a linker script to link in libc++.so: $ cat /usr/lib/libc++.so /* $FreeBSD: projects/clang700-import/lib/libc++/libc++.ldscript 305102 2016-08-31 00:11:35Z bapt $ */ GROUP ( /usr/lib/libc++.so.1 /usr/lib/libcxxrt.so ) and for the static case, we've always just added the relevant .o files from libcxxrt into libc++.a: $ ar tv /usr/lib/libc++.a rw-r--r-- 0/0 21720 Jan 1 01:00 1970 variant.o rw-r--r-- 0/0 61648 Jan 1 01:00 1970 valarray.o rw-r--r-- 0/0 18224 Jan 1 01:00 1970 utility.o rw-r--r-- 0/0 10656 Jan 1 01:00 1970 typeinfo.o rw-r--r-- 0/0 198080 Jan 1 01:00 1970 strstream.o rw-r--r-- 0/0 59264 Jan 1 01:00 1970 shared_mutex.o rw-r--r-- 0/0 231552 Jan 1 01:00 1970 regex.o rw-r--r-- 0/0 96200 Jan 1 01:00 1970 random.o rw-r--r-- 0/0 25240 Jan 1 01:00 1970 optional.o rw-r--r-- 0/0 239552 Jan 1 01:00 1970 iostream.o rw-r--r-- 0/0 17728 Jan 1 01:00 1970 functional.o rw-r--r-- 0/0 219984 Jan 1 01:00 1970 debug.o rw-r--r-- 0/0 58256 Jan 1 01:00 1970 chrono.o rw-r--r-- 0/0 35672 Jan 1 01:00 1970 charconv.o rw-r--r-- 0/0 21280 Jan 1 01:00 1970 bind.o rw-r--r-- 0/0 24312 Jan 1 01:00 1970 any.o rw-r--r-- 0/0 1010288 Jan 1 01:00 1970 algorithm.o rw-r--r-- 0/0 42944 Jan 1 01:00 1970 hash.o rw-r--r-- 0/0 45152 Jan 1 01:00 1970 cxxrt_typeinfo.o rw-r--r-- 0/0 278784 Jan 1 01:00 1970 cxxrt_libelftc_dem_gnu3.o rw-r--r-- 0/0 17704 Jan 1 01:00 1970 cxxrt_stdexcept.o rw-r--r-- 0/0 224664 Jan 1 01:00 1970 thread.o rw-r--r-- 0/0 218392 Jan 1 01:00 1970 future.o rw-r--r-- 0/0 31456 Jan 1 01:00 1970 exception.o rw-r--r-- 0/0 4604424 Jan 1 01:00 1970 locale.o rw-r--r-- 0/0 27216 Jan 1 01:00 1970 vector.o rw-r--r-- 0/0 102712 Jan 1 01:00 1970 mutex.o rw-r--r-- 0/0 63872 Jan 1 01:00 1970 memory.o rw-r--r-- 0/0 1261888 Jan 1 01:00 1970 ios.o rw-r--r-- 0/0 69528 Jan 1 01:00 1970 condition_variable.o rw-r--r-- 0/0 181368 Jan 1 01:00 1970 system_error.o rw-r--r-- 0/0 2006648 Jan 1 01:00 1970 string.o rw-r--r-- 0/0 105408 Jan 1 01:00 1970 stdexcept.o rw-r--r-- 0/0 37552 Jan 1 01:00 1970 new.o rw-r--r-- 0/0 10280 Jan 1 01:00 1970 cxxrt_memory.o rw-r--r-- 0/0 4880 Jan 1 01:00 1970 cxxrt_auxhelper.o rw-r--r-- 0/0 2872 Jan 1 01:00 1970 cxxrt_terminate.o rw-r--r-- 0/0 123504 Jan 1 01:00 1970 cxxrt_exception.o rw-r--r-- 0/0 18136 Jan 1 01:00 1970 cxxrt_dynamic_cast.o rw-r--r-- 0/0 5696 Jan 1 01:00 1970 cxxrt_guard.o But I can link almost all C++ programs statically without having to add `-lpthread`. I guess you only really need it if you start using the multithreading primitives? I'm sort of hesitant to always add if, if it is not always needed. @emaste, what's your opinion on this? Repository: rC Clang https://reviews.llvm.org/D54724 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
