r199632 - Make the Linux support for finding libc++ somewhat less braindead.

[Evgeniy Stepanov]

I don't this adding builddir/lib to linker search path would be right.
Would it make sense to move libc++.so to lib/clang/3.5/lib/linux/?

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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>
>
>
> --
> Alexey Samsonov, MSK
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