<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/56112>56112</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
clang doesn't report full stack trace for static_assert()
</td>
</tr>
<tr>
<th>Labels</th>
<td>
new issue
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
realazthat
</td>
</tr>
</table>
<pre>
When triggering a static_assert within the standard library, clang prints a stack-trace of the instantiation that triggered the assert, but every file/line it lists in the trace is not in user code (rather, it is within stdlib), which makes it extraordinarily difficult to debug ( kinds of traces are very famously difficult to read in the first place, there is no reason to make it nearly impossible!).
In the code below, `const std::optional<std::vector<std::optional<Thing>>> &d = c;` is invalid instantiation because Thing is not copy constructible, and this forces the optional not to be copy constructible, yet the only possible thing to do here is to make a copy, so it asserts.
However, the error does not point to this line, and in a large amount of code I required creduce to pinpoint this.
> All information necessary to reproduce the problem.
> **The reduced test-case that triggers the bug. (symbol.cxx):**
```
#include <vector>
#include <optional>
struct Thing {
Thing() = delete;
Thing(const Thing&) = delete;
Thing& operator=(const Thing&) = delete;
Thing& operator=( Thing&&);
Thing(Thing&&);
};
void b() {
std::vector<std::optional<Thing>> c;
// The following line instantiates the static_assert failure,
// but it is not listed in the error.
const std::optional<std::vector<std::optional<Thing>>> &d = c;
}
```
* **Command and output**
```bash
$clang-14 symbol.cxx -std=c++20`
In file included from symbol.cxx:2:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/vector:66:
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:138:7: error: static_assert failed due to requirement 'is_constructible<std::optional<Thing>, const std::optional<Thing> &>::value' "result type must be constructible from value type of input range"
static_assert(is_constructible<_ValueType2, decltype(*__first)>::value,
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:333:19: note: in instantiation of function template specialization 'std::uninitialized_copy<__gnu_cxx::__normal_iterator<const std::optional<Thing> *, std::vector<std::optional<Thing>>>, std::optional<Thing> *>' requested here
{ return std::uninitialized_copy(__first, __last, __result); }
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_vector.h:558:9: note: in instantiation of function template specialization 'std::__uninitialized_copy_a<__gnu_cxx::__normal_iterator<const std::optional<Thing> *, std::vector<std::optional<Thing>>>, std::optional<Thing> *, std::optional<Thing>>' requested here
std::__uninitialized_copy_a(__x.begin(), __x.end(),
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/optional:225:8: note: in instantiation of member function 'std::vector<std::optional<Thing>>::vector' requested here
: _M_value(std::forward<_Args>(__args)...)
^
In file included from symbol.cxx:2:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/vector:62:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_algo.h:62:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_tempbuf.h:60:
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_construct.h:109:38: error: call to implicitly-deleted copy constructor of 'std::optional<Thing>'
{ ::new(static_cast<void*>(__p)) _Tp(std::forward<_Args>(__args)...); }
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:92:8: note: in instantiation of function template specialization 'std::_Construct<std::optional<Thing>, const std::optional<Thing> &>' requested here
std::_Construct(std::__addressof(*__cur), *__first);
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:151:2: note: in instantiation of function template specialization 'std::__uninitialized_copy<false>::__uninit_copy<__gnu_cxx::__normal_iterator<const std::optional<Thing> *, std::vector<std::optional<Thing>>>, std::optional<Thing> *>' requested here
__uninit_copy(__first, __last, __result);
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:333:19: note: in instantiation of function template specialization 'std::uninitialized_copy<__gnu_cxx::__normal_iterator<const std::optional<Thing> *, std::vector<std::optional<Thing>>>, std::optional<Thing> *>' requested here
{ return std::uninitialized_copy(__first, __last, __result); }
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_vector.h:558:9: note: in instantiation of function template specialization 'std::__uninitialized_copy_a<__gnu_cxx::__normal_iterator<const std::optional<Thing> *, std::vector<std::optional<Thing>>>, std::optional<Thing> *, std::optional<Thing>>' requested here
std::__uninitialized_copy_a(__x.begin(), __x.end(),
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/optional:225:8: note: in instantiation of member function 'std::vector<std::optional<Thing>>::vector' requested here
: _M_value(std::forward<_Args>(__args)...)
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/optional:665:7: note: copy constructor of 'optional<Thing>' is implicitly deleted because base class '_Enable_copy_move<is_copy_constructible_v<Thing>, __and_v<is_copy_constructible<Thing>, is_copy_assignable<Thing>>, is_move_constructible_v<Thing>, __and_v<is_move_constructible<Thing>, is_move_assignable<Thing>>, optional<Thing>>' has a deleted copy constructor
private _Enable_copy_move<
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/enable_special_members.h:159:15: note: '_Enable_copy_move' has been explicitly marked deleted here
constexpr _Enable_copy_move(_Enable_copy_move const&) noexcept = delete;
^
2 errors generated.
```
> **The location where you obtained LLVM (if not from our Git repository).**
* **clang is installed from `apt`.**
```
$apt show clang-14 -a
Package: clang-14
Version: 1:14.0.5-1~kisak~f
Priority: optional
Section: devel
Source: llvm-toolchain-14
Maintainer: LLVM Packaging Team <pkg-llvm-team@lists.alioth.debian.org>
Installed-Size: 370 kB
Provides: c++-compiler, c-compiler, objc-compiler
Depends: libc6 (>= 2.14), libclang-cpp14 (>= 1:14.0.5), libgcc-s1 (>= 3.0), libllvm14, libstdc++6 (>= 5.2), libstdc++-9-dev, libgcc-9-dev, libobjc-9-dev, libclang-common-14-dev (= 1:14.0.5-1~kisak~f), llvm-14-linker-tools (= 1:14.0.5-1~kisak~f), libclang1-14 (= 1:14.0.5-1~kisak~f), libc6-dev, binutils
Recommends: llvm-14-dev, python3
Suggests: clang-14-doc
Download-Size: 126 kB
APT-Sources: http://ppa.launchpad.net/kisak/kisak-mesa/ubuntu focal/main amd64 Packages
Description: C, C++ and Objective-C compiler
Clang project is a C, C++, Objective C and Objective C++ front-end
based on the LLVM compiler. Its goal is to offer a replacement to the
GNU Compiler Collection (GCC).
.
Clang implements all of the ISO C++ 1998, 11, 14 and 17 standards and also
provides most of the support of C++20.
Package: clang-14
Version: 1:14.0.1-1~kisak1~f
Status: install ok installed
Priority: optional
Section: devel
Source: llvm-toolchain-14
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: LLVM Packaging Team <pkg-llvm-team@lists.alioth.debian.org>
Installed-Size: 370 kB
Provides: c++-compiler, c-compiler, objc-compiler
Depends: libc6 (>= 2.14), libclang-cpp14 (>= 1:14.0.1), libgcc-s1 (>= 3.0), libllvm14, libstdc++6 (>= 5.2), libstdc++-9-dev, libgcc-9-dev, libobjc-9-dev, libclang-common-14-dev (= 1:14.0.1-1~kisak1~f), llvm-14-linker-tools (= 1:14.0.1-1~kisak1~f), libclang1-14 (= 1:14.0.1-1~kisak1~f), libc6-dev, binutils
Recommends: llvm-14-dev, python3
Suggests: clang-14-doc
Homepage: https://www.llvm.org/
Download-Size: unknown
APT-Manual-Installed: yes
APT-Sources: /var/lib/dpkg/status
Description: C, C++ and Objective-C compiler
Clang project is a C, C++, Objective C and Objective C++ front-end
based on the LLVM compiler. Its goal is to offer a replacement to the
GNU Compiler Collection (GCC).
.
Clang implements all of the ISO C++ 1998, 11, 14 and 17 standards and also
provides most of the support of C++20.
```
* **clang version:**
```bash
$ clang-14 --version
Ubuntu clang version 14.0.1-1~kisak1~f
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
```
* OS: Ubuntu over WSL (Windows Subsystem for Linux)
* **lsb_release -a**
```
$lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.4 LTS
Release: 20.04
Codename: focal
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJztWltz46gS_jXOCyWVJd-Shzw4dmY3VZmdrZPszKMKSdhmjYQOSHa8v_50A7o5zu2cndueuBzFQk3TNF9_NIJYpofLLxuWk1Lx9Zopnq8JJbqkJU8iqjVTJdnzcsNBYsPwQZ5SlRLBY0XVYRAuSCIoVCqgaqlt3WTrlYomjMiVqcVzrFdyUCpRDy3r5lhqBGxDqCyuSsJ2TB3Iigs2CD8InoOCEhrUoN6ZYbVzTXJZYlkF1UkiU0YG4bmiIKJQGVQDGWe-LlMwehBe4JP9hicbktEt0yjFHkCjVCnPqeLiQFK-WvGkEmCnJCmLqzUqJluep9p0CtuHzipGrK00k5U-rqgYTWuLV1zpkhQC6mH7aKHrAIppdIs09qA5OaMKlPGskFrzGP0QgOH-YLgcDOf2emP1mk7HTMg9qh1Mh4kEZ2NnB6M5fGWBPqdiMFo0ZTuWlFJ1SzpS9-Cr9WB0bb_Q7WlKBqMlSQajK1CPNvN8RwVPj4Y1ZgmFcSBGQT02iSwOxJikqqS0XVkQwBAYDyIrqdCP2JHaBFMNfBGzJyofWGkr5OCi2kGoDlrF0ZKk9m3tUWo0YV0t0b0Wbbrnzl_lHmHnxoYwpaQCXcx2o5AAbtRnrEZI1t2A4aVEULWGZgADIAXwMINyAwP774ojxBO4VABYUFDw3CkDTT0L3BV8PhcC9IJvMuvZnIGTNESbBVWhpNUGdsJv6H3mH6sYhHP43oOEbRr8zXTpJVSzXvxZ3wO-fQS4PmSxFH7y8IBhMppbLcSpnQ7d196GI54nosKYGy1qSF2fetii6_pxh-3gOtQMZle2lNgCsAksMfhLmWAlQxAeCVjAu7vpS-JTABoDhkBjl_9z7U7FqXHZI-ueEBjMlu1vc91JiKi47nDrhzdHrY1UVxsIFL4EgbCSAlgCvWwptQleF4B9zl9RLiqFMD9ShQRteRUDA1mZNSRnosavK3xVJmq8eBqbcxcBC5llGKb4J6uyqEpbflQtpnpTVx2b-cwLxqQNB-IZA5fJILyCb9g2BTSMExVxcE_JSsmsUxO6FGLPnhEGr1YamOdDzHO4-r6Z9QAKH9YJNPjh4XwaTccejFr14K3zCoqCoBY8ujjN8MuZWgvXnp5Pp40536ThmJca_ulSRFXOcw6IE_wvlvobsCMYncN1Bn8WO_jjMQ7BUWnFLPkZRs0YEOggnHEd9aeHF4CEycqToKylEGgGcgagVFTQqRkUhoppM7EfCkayCrSYKarTvB1OU8VKwVQAdA8BowBRoCasQwM_vX5C3J_oTPQZdd2DqhBtT1kiUK8hiXkUmZzCsErf2kW3mcHkmnQ_g9n1z_H9QSA6Go0QqDgdIuMx_A901899YKBXVZ7Y9JZlkOaVQKgFS4wmKwMoamDXayYy2QmMdgQdiCxnwDeKcswARMTLespZvAq9c5Pp_BcU26v3lG4Um5lAZIb6Mdlq8QYTFzwrK5WT5zobnjfoXZAoErT-ZWPMzpSkoXfy6AOo_j4Ase40yJhMkLz-XmBE0WNvRfSnAccLMi-Ap-bF532B2HnwY7bGAT936zksYnnaFJzEzbcFTdv_eRhO4Hr-ElIylsWwjm0A0wXG60eqI_2ir8EnYEv0MXIzx3mjHVYfe1jnI_Lmaq3NyIHjKf6GlSh2_eKUkxsf_3yJ0Q9hTodqqFhLQzQ_nGXIZHG1ssYNv1s-2aRLNpccIhWbhLJNJhMKa2lIHDlQL094KQ6eXdulR28XYLUPEdiNuJMJ5Kw_1VnJnO1N6Jh8LsG5DBbEsJyrp0uIm8LQ0gWJ7os3R9nzM-GJj035_rEZ2UX4GjJ927S7qHHwty4hXsG__RmvNaMDEsBDmkJipOWqzvyTSrmJ72ghcPUMTL5bznRi3TcJHP9_3dQJxmRFhWbNxFgL_ZNybvz0-_Wq9Lqv4AcCx_uK633F9b7iel9xva-43rbi-tY-nk7Rx7Ouj5_IqU-n0mYrscnLSZ2X1_uIMe5VJUBUGlVE1zmNBbOQzOQOX4-aN6Zw23ttGu2O0jVwYZ6a0pPyR9K1DDTL16bJ42gyMmjBW9p9LP-4XSPzXLtPx_eG4s77UyubLmoKxXfIiKf8efTa-NvTPbM2ObaObHRqlzFemGsXbSdh4bwRM5YT9tCgK6Nqi_sIzkX90DS-AmF1wi0Qg8dlVt5tF-aSPSSsKMnpjcOTkRraBaoma5bjZAKJz-l9rBP7uUImlr72Zpv7ICsi45LyHHp1e_v5I-7j8pXZnDPvBmSlyC-8xH1jqTmg4WBOEnR2wXBrz17gaw9zmE1-4EohmlcM0yEtSrj6JzfQms0zECJ6I_ek2UXzqH34O022dG1pwj2zDz7DGEOH8AGuCoKxP_QnXgArzi3XdAv_V06D4lLx8oCSTSyYJ3fM8Dc-SNmO1aXQ98Q0KMQu80opRbIBTzUtf4Qb4zrzrsB4z1qJu6T3jGa4e11s156tDwWD8dAcRPFhhpTlxk9ZzGnuS7VuNrdvasd5dzCJouLRbEi2V3Uf5I6nTBs32CDwEpkVXNjDB0nvTsZ_dgqMgiUrYNo19SEMkymOtyGCJQl96JidnfGRcXJSFDAGrUzr4VYSAtnTQUdo5A_bp9h31GtuYLZyVncbnvhhK9-KeBcejEanke696Vq3wNkrs0ziCOET28TyaVi4RnF0AsNBW6bMOOvXVnXtBl7tpVdVmdZ2AylWJRfajs2_GJrfDI8zy4kWh3Ij85GDZrVeQ5Kgu9HgpTJxYyz3uZC0RVAQThsEzX-_9yyyTe1NWRaYQJjd-aKgvqCQzWwKmvo5A5L6YO13_72MaYqUHld5WZEVkImA24ziOZYsnY5dADBdo00nihd1cC2wIws7umZP_VP8J4bejnn4XqSLU7Jwx8IkSiCj0F51_NnUJou-tqYN4J689DDPtEoxKUiJtMcNTMDWrfrkpgRClVS4oz9ytYLUjiLx4akrs2dsTvDUxP_Lb3-QhasNPyBk6yTw_JfFoj1vRfxejzBlMdqgR0LUR9xu7j41RgcXF-fYPZza4Do2fQtmzeE5bQqo0NIpLhwpkEzqstaoq6KQytwu6mMHvXM-byLUoMVy0DLqXUnLStvs2LAWkduW-b8J6_5hkbhEBXi4RiPnWnh6RquXcp1UWjfUax_6MPAN535SHDibCu__mdGDn5HRH-HyDZT-VN3nOP2ZOl-Z1H-VGStcvCJp64a19_u9j3oN6KDk9BxQ5dscytpJ4CPNK4B8g04UOtTEfTRLgNodVU3qnkIImNcrJvzfmf6HZXry5Mk2m6jvGqp_-VxbJyX36nrmmaPgnkbyzKxxj8ddS0SJW_wVSWf9Z0U25vBzJmFBhIK49ng4YtMlVw6a7QLzqdN8n-46cwUswRT5cneL4_eF56nca3JXxfoAi7gMzxSTW7TGHKQ88prQcaRgjYbvFmBh8uxS5kjWFP8mye3dFfarEu4AON1RLnCB6IZsCbOJ4nGFrz9ulq3ZJ8MMPq5TMOTDsT8mt_d3Ne-Ypp0UfoyIfbgAx-Y06zy1qVy_K2fp5Si9GF3QsxIWwezSjjCeaoal_MyuCfGMXQXoNsf23cF6dOHx8TTw5lmlxGWfuta83FSxmYuBW4DD3D_PsQEu-rWuGK7uJ9MgCM82l0EyO1_RIBjGIwjcYHzOktF4ErDhxSgexUN6Bt5kQl8OJhAKYc72xKjA43OT5Rm_DIdhOJwGF8NZGIQzn8arKdyFwWw4SdlsDBM6g3xWNJR6pi6NSXG1bpOI5qF94cKYaQ700woYXV0CfAX9C49Kn5nWL431_wGwutha">