Hi,
Crazy question, but would someone kind be able to help me a little here. I have
a clang 4.0 installation on my linux laptop, which crashes when compiling this
code fragment:
template <const int& X>
constexpr auto fn1() { return X; }
template <typename>
auto fn2()
{
return ([]() {
static constexpr auto value = 12;
return fn1<value>();
})();
}
auto test()
{
return fn2<int>();
}
However, doing the same on the godbolt clang 4.0.0 compiler doesn't crash. What
I can't work out is why!?
The is the command I run on my machine (using a clean checkout from the clang
svn repository) and the output given (the problem seems to be a non-instantiated
VarDecl in "LocalInstantiationScope::findInstantiationOf()" if you add debug
information to the compiler code at this point):
$ ~/Toolchains/clang-4.0/bin/clang++ -std=c++1z -O2 -S -o - test.cpp -v
clang version 4.0.0 (branches/release_40)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/user/Toolchains/clang-4.0/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.3.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.3.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/home/user/Toolchains/clang-4.0/bin/clang-4.0" -cc1 -triple
x86_64-unknown-linux-gnu -S -disable-free -main-file-name test.cpp
-mrelocation-model static -mthread-model posix -fmath-errno -masm-verbose
-mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64
-momit-leaf-frame-pointer -v -dwarf-column-info -debugger-tuning=gdb
-coverage-notes-file /home/user/test/-.gcno -resource-dir
/home/user/Toolchains/clang-4.0/bin/../lib/clang/4.0.0 -internal-isystem
/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0
-internal-isystem
/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0
-internal-isystem
/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0
-internal-isystem
/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward
-internal-isystem /usr/local/include -internal-isystem
/home/user/Toolchains/clang-4.0/bin/../lib/clang/4.0.0/include
-internal-externc-isystem /usr/include/x86_64-linux-gnu
-internal-externc-isystem /include -internal-externc-isystem /usr/include -O2
-std=c++1z -fdeprecated-macro -fdebug-compilation-dir /home/user/test
-ferror-limit 19 -fmessage-length 92 -fobjc-runtime=gcc -fcxx-exceptions
-fexceptions -fdiagnostics-show-option -fcolor-diagnostics -vectorize-loops
-vectorize-slp -o - -x c++ test.cpp
clang -cc1 version 4.0.0 based upon LLVM 4.0.0 default target
x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
ignoring duplicate directory
"/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0
/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0
/usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward
/usr/local/include
/home/user/Toolchains/clang-4.0/bin/../lib/clang/4.0.0/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
clang-4.0:
/home/user/Toolchains/clang-4.0/source/tools/clang/lib/Sema/
SemaTemplateInstantiate.cpp:2814: llvm::PointerUnion<Decl *,
LocalInstantiationScope::DeclArgumentPack *>
*clang::LocalInstantiationScope::findInstantiationOf(const clang::Decl *):
Assertion `isa<LabelDecl>(D) && "declaration not instantiated in this scope"'
failed.
0 clang-4.0 0x0000000001ac29e5
llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1 clang-4.0 0x0000000001ac30b6
2 libpthread.so.0 0x00007f1fd115a0c0
3 libc.so.6 0x00007f1fcfceffff gsignal + 207
4 libc.so.6 0x00007f1fcfcf142a abort + 362
5 libc.so.6 0x00007f1fcfce8e67
6 libc.so.6 0x00007f1fcfce8f12
7 clang-4.0 0x0000000002f0ecb4
clang::LocalInstantiationScope::findInstantiationOf(clang::Decl const*) + 516
8 clang-4.0 0x0000000002f2f815
clang::Sema::FindInstantiatedDecl(clang::SourceLocation, clang::NamedDecl*,
clang::MultiLevelTemplateArgumentList const&) + 181
[...]
The same output from the godbolt compiler gives...
clang version 4.0.0 (tags/RELEASE_400/final 299826)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-4.0.0/bin
Found candidate GCC installation:
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0
Selected GCC installation:
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/opt/compiler-explorer/clang-4.0.0/bin/clang-4.0" -cc1 -triple
x86_64-unknown-linux-gnu -S -disable-free -disable-llvm-verifier
-discard-value-names -main-file-name example.cpp -mrelocation-model static
-mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases
-munwind-tables -fuse-init-array -target-cpu x86-64 -momit-leaf-frame-pointer -v
-dwarf-column-info -debug-info-kind=limited -dwarf-version=4
-debugger-tuning=gdb -coverage-notes-file
/tmp/compiler-explorer-compiler118118-58-1f6fedy.0ym1/output.gcno -resource-dir
/opt/compiler-explorer/clang-4.0.0/bin/../lib/clang/4.0.0 -internal-isystem
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0/../../../../
include/c++/7.2.0 -internal-isystem
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0/../../../../
include/c++/7.2.0/x86_64-linux-gnu -internal-isystem
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0/../../../../
include/c++/7.2.0/backward -internal-isystem /usr/local/include
-internal-isystem
/opt/compiler-explorer/clang-4.0.0/bin/../lib/clang/4.0.0/include
-internal-externc-isystem /usr/include/x86_64-linux-gnu
-internal-externc-isystem /include -internal-externc-isystem /usr/include -O2
-std=c++1z -fdeprecated-macro -fdebug-compilation-dir
/tmp/compiler-explorer-compiler118118-58-1f6fedy.0ym1 -ferror-limit 19
-fmessage-length 0 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions
-fdiagnostics-show-option -fcolor-diagnostics -vectorize-loops -vectorize-slp
-mllvm --x86-asm-syntax=intel -o
/tmp/compiler-explorer-compiler118118-58-1f6fedy.0ym1/output.s -x c++ <source>
clang -cc1 version 4.0.0 based upon LLVM 4.0.0 default target
x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0/../../../../
include/c++/7.2.0
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0/../../../../
include/c++/7.2.0/x86_64-linux-gnu
/opt/compiler-explorer/gcc-7.2.0/lib/gcc/x86_64-linux-gnu/7.2.0/../../../../
include/c++/7.2.0/backward
/usr/local/include
/opt/compiler-explorer/clang-4.0.0/bin/../lib/clang/4.0.0/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
Compiler returned: 0
Does anyone have an ideas why my compiler should crash? Would anybody please be
able to test my fragment and report if they also have a crash like me. I've
tried the 6.0.0 compiler too with the same results on my machine. I'm building
the 7.0.0 compiler now to see if the problem still occurs, but it looks like it
does (based on the rc-compiler I had already built).
(I have a bug report 39916 for a similar issue, but the code in the bug report
also exhibits problems on godbolt as well as my local compiler, producing both
invalid code and compiler crashes so I don't think this is an isolated problem.)
Any help would be gratefully received -- I am pulling my hair out trying to get
this code to work :o)
Thanks,
Andy
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