r199632 - Make the Linux support for finding libc++ somewhat less braindead.
Chandler Carruth
chandlerc at google.com
Tue Jan 21 01:06:30 PST 2014
On Tue, Jan 21, 2014 at 12:06 AM, Evgeniy Stepanov <
eugeni.stepanov at gmail.com> wrote:
> I don't this adding builddir/lib to linker search path would be right.
>
Why not?
> Would it make sense to move libc++.so to lib/clang/3.5/lib/linux/?
>
This is a good question.
Historically, GCC has considered libstdc++ to be "part of" the compiler or
toolchain, and distributed them together. We lookup libstdc++ out of GCC's
installation tree for example.
Also historically, libc++ has *not* been distributed as "part of" the
compiler or toolchain. On OS X it is actually more part of the OS than the
toolchain. Even on Linux, some care has been taken to try to make it
effective to use libc++ with a GCC host just as much as with a Clang host.
I'm not trying to endorse either of these approaches, but that's what they
have been historically. To my mind, that makes lib/clang/<version>
inapropriate for libc++. If we want to switch to shipping libc++ as merely
an implementation detail of Clang itself, then I would suggest installing
*both* headers and libraries under lib/clang/<version>. But that would be a
reasonably radical departure from current trends etc.
>
> On Mon, Jan 20, 2014 at 7:23 PM, Alexey Samsonov <samsonov at google.com>
> wrote:
> > Hi Chandler,
> >
> > Fixing include paths is not enough - you should also fix library
> > lookup paths for dynamic linker in Clang driver. Currently if the
> > build tree has both Clang binary and built libc++ like this:
> > <...>/bin/clang++
> > <...>/lib/libc++.so
> >
> > Clang binary is not able to locate libc++.so with -stdlib=libc++
> > provided. Therefore the following brute-force bootstrap process
> > wouldn't work:
> > (1) configure a new build tree with default options and build Clang and
> libc++
> > (2) configure a new build tree with just-built Clang as c/c++ compiler
> > and specify LLVM_ENABLE_LIBCXX=ON
> >
> > I'll try to take a closer look at this (and potentially fix the
> > driver) tomorrow, unless someone who has more understanding picks it
> > up from here.
> >
> >
> >
> > On Mon, Jan 20, 2014 at 1:42 PM, Chandler Carruth <chandlerc at gmail.com>
> wrote:
> >> Author: chandlerc
> >> Date: Mon Jan 20 03:42:24 2014
> >> New Revision: 199632
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=199632&view=rev
> >> Log:
> >> Make the Linux support for finding libc++ somewhat less braindead.
> >>
> >> Now instead of just looking in the system root for it, we also look
> >> relative to the clang binary's directory. This should "just work" in
> >> almost all cases. I've added test cases accordingly.
> >>
> >> This is probably *very* worthwhile to backport to the 3.4 branch so that
> >> folks can check it out, build it, and use that as their host compiler
> >> going forward.
> >>
> >> Modified:
> >> cfe/trunk/lib/Driver/ToolChains.cpp
> >> cfe/trunk/test/Driver/linux-header-search.cpp
> >>
> >> Modified: cfe/trunk/lib/Driver/ToolChains.cpp
> >> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/ToolChains.cpp?rev=199632&r1=199631&r2=199632&view=diff
> >>
> ==============================================================================
> >> --- cfe/trunk/lib/Driver/ToolChains.cpp (original)
> >> +++ cfe/trunk/lib/Driver/ToolChains.cpp Mon Jan 20 03:42:24 2014
> >> @@ -2945,9 +2945,24 @@ void Linux::AddClangCXXStdlibIncludeArgs
> >>
> >> // Check if libc++ has been enabled and provide its include paths if
> so.
> >> if (GetCXXStdlibType(DriverArgs) == ToolChain::CST_Libcxx) {
> >> - // libc++ is always installed at a fixed path on Linux currently.
> >> - addSystemInclude(DriverArgs, CC1Args,
> >> - getDriver().SysRoot + "/usr/include/c++/v1");
> >> + const std::string LibCXXIncludePathCandidates[] = {
> >> + // The primary location is within the Clang installation.
> >> + // FIXME: We shouldn't hard code 'v1' here to make Clang future
> proof to
> >> + // newer ABI versions.
> >> + getDriver().Dir + "/../include/c++/v1",
> >> +
> >> + // We also check the system as for a long time this is the only
> place Clang looked.
> >> + // FIXME: We should really remove this. It doesn't make any
> sense.
> >> + getDriver().SysRoot + "/usr/include/c++/v1"
> >> + };
> >> + for (unsigned i = 0; i <
> llvm::array_lengthof(LibCXXIncludePathCandidates);
> >> + ++i) {
> >> + if (!llvm::sys::fs::exists(LibCXXIncludePathCandidates[i]))
> >> + continue;
> >> + // Add the first candidate that exists.
> >> + addSystemInclude(DriverArgs, CC1Args,
> LibCXXIncludePathCandidates[i]);
> >> + break;
> >> + }
> >> return;
> >> }
> >>
> >> @@ -2971,7 +2986,7 @@ void Linux::AddClangCXXStdlibIncludeArgs
> >> MIPSABIDirSuffix, DriverArgs, CC1Args))
> >> return;
> >>
> >> - const std::string IncludePathCandidates[] = {
> >> + const std::string LibStdCXXIncludePathCandidates[] = {
> >> // Gentoo is weird and places its headers inside the GCC install,
> so if the
> >> // first attempt to find the headers fails, try these patterns.
> >> InstallDir.str() + "/include/g++-v" + Version.MajorStr + "." +
> >> @@ -2984,8 +2999,9 @@ void Linux::AddClangCXXStdlibIncludeArgs
> >> LibDir.str() + "/../include/c++",
> >> };
> >>
> >> - for (unsigned i = 0; i <
> llvm::array_lengthof(IncludePathCandidates); ++i) {
> >> - if (addLibStdCXXIncludePaths(IncludePathCandidates[i],
> >> + for (unsigned i = 0; i <
> llvm::array_lengthof(LibStdCXXIncludePathCandidates);
> >> + ++i) {
> >> + if (addLibStdCXXIncludePaths(LibStdCXXIncludePathCandidates[i],
> >> TripleStr + MIPSABIDirSuffix +
> BiarchSuffix,
> >> DriverArgs, CC1Args))
> >> break;
> >>
> >> Modified: cfe/trunk/test/Driver/linux-header-search.cpp
> >> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/linux-header-search.cpp?rev=199632&r1=199631&r2=199632&view=diff
> >>
> ==============================================================================
> >> --- cfe/trunk/test/Driver/linux-header-search.cpp (original)
> >> +++ cfe/trunk/test/Driver/linux-header-search.cpp Mon Jan 20 03:42:24
> 2014
> >> @@ -1,6 +1,29 @@
> >> // General tests that the header search paths detected by the driver
> and passed
> >> // to CC1 are sane.
> >> //
> >> +// Test a simulated installation of libc++ on Linux, both through
> sysroot and
> >> +// the installation path of Clang.
> >> +// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
> >> +// RUN: -target x86_64-unknown-linux-gnu \
> >> +// RUN: -stdlib=libc++ \
> >> +// RUN: -ccc-install-dir %S/Inputs/basic_linux_tree/usr/bin \
> >> +// RUN: --sysroot=%S/Inputs/basic_linux_libcxx_tree \
> >> +// RUN: | FileCheck --check-prefix=CHECK-BASIC-LIBCXX-SYSROOT %s
> >> +// CHECK-BASIC-LIBCXX-SYSROOT: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
> >> +// CHECK-BASIC-LIBCXX-SYSROOT: "-isysroot" "[[SYSROOT:[^"]+]]"
> >> +// CHECK-BASIC-LIBCXX-SYSROOT: "-internal-isystem"
> "[[SYSROOT]]/usr/include/c++/v1"
> >> +// CHECK-BASIC-LIBCXX-SYSROOT: "-internal-isystem"
> "[[SYSROOT]]/usr/local/include"
> >> +// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
> >> +// RUN: -target x86_64-unknown-linux-gnu \
> >> +// RUN: -stdlib=libc++ \
> >> +// RUN: -ccc-install-dir %S/Inputs/basic_linux_libcxx_tree/usr/bin
> \
> >> +// RUN: --sysroot=%S/Inputs/basic_linux_libcxx_tree \
> >> +// RUN: | FileCheck --check-prefix=CHECK-BASIC-LIBCXX-INSTALL %s
> >> +// CHECK-BASIC-LIBCXX-INSTALL: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
> >> +// CHECK-BASIC-LIBCXX-INSTALL: "-isysroot" "[[SYSROOT:[^"]+]]"
> >> +// CHECK-BASIC-LIBCXX-INSTALL: "-internal-isystem"
> "[[SYSROOT]]/usr/bin/../include/c++/v1"
> >> +// CHECK-BASIC-LIBCXX-INSTALL: "-internal-isystem"
> "[[SYSROOT]]/usr/local/include"
> >> +//
> >> // Test a very broken version of multiarch that shipped in Ubuntu
> 11.04.
> >> // RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
> >> // RUN: -target i386-unknown-linux \
> >>
> >>
> >> _______________________________________________
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> >> cfe-commits at cs.uiuc.edu
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> >
> >
> >
> > --
> > Alexey Samsonov, MSK
> > _______________________________________________
> > cfe-commits mailing list
> > cfe-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
> _______________________________________________
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