Segfault with template-template in function

[anarthal]

Code:

namespace repro {

template <template <class...> class ListType>
constexpr void f(ListType<int>)
{
}

}  // namespace repro

int main() {}

Segfaults:

/usr/include/c++/14/bits/unique_ptr.h:447: typename std::add_lvalue_reference<_Tp>::type std::unique_ptr<_Tp, _Dp>::operator*() const [with _Tp = clang::mrdocs::TypeInfo; _Dp = std::default_delete<clang::mrdocs::TypeInfo>; typename std::add_lvalue_reference<_Tp>::type = clang::mrdocs::TypeInfo&]: Assertion 'get() != pointer()' failed.
PLEASE submit a bug report to https://github.com/cppalliance/mrdocs/issues/ and include the crash backtrace.
 #0 0x000000000327dc20 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/mrdocs-0.0.3/bin/mrdocs+0x327dc20)
 #1 0x000000000327ab9b SignalHandler(int) Signals.cpp:0:0
 #2 0x00000000033a87b0 __restore_rt libc_sigaction.o:0:0
 #3 0x00000000033cc35c __pthread_kill (/opt/mrdocs-0.0.3/bin/mrdocs+0x33cc35c)
 #4 0x00000000033a872e raise (/opt/mrdocs-0.0.3/bin/mrdocs+0x33a872e)
 #5 0x000000000043cb39 abort (/opt/mrdocs-0.0.3/bin/mrdocs+0x43cb39)
 #6 0x00000000032aefed (/opt/mrdocs-0.0.3/bin/mrdocs+0x32aefed)
 #7 0x00000000005b2f57 clang::mrdocs::TagfileWriter::writeFunctionMember(clang::mrdocs::FunctionInfo const&) (/opt/mrdocs-0.0.3/bin/mrdocs+0x5b2f57)
 #8 0x00000000005bc738 clang::mrdocs::TagfileWriter::writeNamespace(clang::mrdocs::NamespaceInfo const&) (/opt/mrdocs-0.0.3/bin/mrdocs+0x5bc738)
 #9 0x00000000005bc5bc clang::mrdocs::TagfileWriter::writeNamespace(clang::mrdocs::NamespaceInfo const&) (/opt/mrdocs-0.0.3/bin/mrdocs+0x5bc5bc)
#10 0x00000000005bd838 clang::mrdocs::TagfileWriter::build() (/opt/mrdocs-0.0.3/bin/mrdocs+0x5bd838)
#11 0x0000000000586fa2 clang::mrdocs::hbs::HandlebarsGenerator::build(std::basic_string_view<char, std::char_traits<char>>, clang::mrdocs::Corpus const&) const (/opt/mrdocs-0.0.3/bin/mrdocs+0x586fa2)
#12 0x00000000005418ec clang::mrdocs::Generator::build(clang::mrdocs::Corpus const&) const (/opt/mrdocs-0.0.3/bin/mrdocs+0x5418ec)
#13 0x000000000049616a clang::mrdocs::DoGenerateAction(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&, clang::mrdocs::ReferenceDirectories const&, char const**) (/opt/mrdocs-0.0.3/bin/mrdocs+0x49616a)
#14 0x000000000049cf33 clang::mrdocs::mrdocs_main(int, char const**) (/opt/mrdocs-0.0.3/bin/mrdocs+0x49cf33)
#15 0x000000000043d42d main (/opt/mrdocs-0.0.3/bin/mrdocs+0x43d42d)
#16 0x000000000338f7b8 __libc_start_call_main libc-start.o:0:0
#17 0x0000000003391980 __libc_start_main (/opt/mrdocs-0.0.3/bin/mrdocs+0x3391980)
#18 0x000000000048cda5 _start (/opt/mrdocs-0.0.3/bin/mrdocs+0x48cda5)

[alandefreitas]

Unfortunately, that doesn't reproduce the issue.

repro::f

Synopsis

Declared in <function-template-template.cpp>

template<template<class...> typename ListType>
constexpr
void
f();

Fortunately, the error is in this tagfile generation #795 and it's the same for #794. I'll adapt the tagfile generator to test these cases.

[alandefreitas]

OK. I figured this out. MrDocs can correctly extract the template parameter but not the function parameter. That's why the documentation says f() and not f(ListType<int>). When rendering the templates, the missing parameter (nullptr) becomes undefined and that's it. In the tagfile generator, it tries to render the nullptr and that's a segmentation fault. So it's just a feature we have to implement.

[anarthal]

Just to be clear: I don't need this done - the code that raised this is private. I reported because it was a segfault.

[anarthal]

BTW - would it make sense somehow attaching version information to MrDocs crashes, so reporting is easier? ATM, running mrdocs --version only outputs a semver string (no build number).

[alandefreitas]

BTW - would it make sense somehow attaching version information to MrDocs crashes, so reporting is easier? ATM, running mrdocs --version only outputs a semver string (no build number).

Yes. We need to improve this. Whenever we report an error, we include the version and the build:

mrdocs/src/lib/Support/Error.cpp

Lines 257 to 260 in e068292

	os << "An issue occurred during execution.\n";
	os << "If you believe this is a bug, please report it at https://github.com/cppalliance/mrdocs/issues\n"
	"with the following details:\n";
	os << fmt::format(" MrDocs Version: {} (Build: {})\n", project_version, project_version_build);

We don't report it in this case because it's an exception, which uses the llvm handle. We need to change this handle or use the same report::error for these exceptions.