<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/112737>112737</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang++] Assertion `!isa<NamedDecl>(static_cast<decl_type*>(this)) || cast<NamedDecl>(static_cast<decl_type*>(this))->isLinkageValid()' failed.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:frontend,
            crash-on-valid,
            clang:frontend:fuzzer
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          yijan4845
      </td>
    </tr>
</table>

<pre>
    **This testcase is generated by a fuzzer.**

Compiler Explorer: [https://godbolt.org/z/73KjnYb3j](https://godbolt.org/z/73KjnYb3j)

This invalid code will crash on Clang Assertion Trunk, it seems that this goes back to clang-3.7:
```cpp
#pragma redefine_extname foo_cpp bar_cpp
static int foo_cpp();
extern int foo_cpp() { return 1; }
```

Stack dump:
```
clang++: /root/llvm-project/clang/include/clang/AST/Decl.h:5011: void clang::Redeclarable<decl_type>::setPreviousDecl(decl_type*) [with decl_type = clang::FunctionDecl]: Assertion `!isa<NamedDecl>(static_cast<decl_type*>(this)) || cast<NamedDecl>(static_cast<decl_type*>(this))->isLinkageValid()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics <source>
1.      <source>:3:22: current parser token '{'
 #0 0x0000000003bb1d58 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bb1d58)
 #1 0x0000000003bafa1c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bafa1c)
 #2 0x0000000003afcd68 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007ddbe3c42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007ddbe3c969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007ddbe3c42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007ddbe3c287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007ddbe3c2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007ddbe3c39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x00000000078f6c4d clang::Redeclarable<clang::FunctionDecl>::setPreviousDecl(clang::FunctionDecl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x78f6c4d)
#10 0x0000000007a5b4e3 clang::FunctionDecl::setPreviousDeclaration(clang::FunctionDecl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x7a5b4e3)
#11 0x0000000006a34430 clang::Sema::CheckFunctionDeclaration(clang::Scope*, clang::FunctionDecl*, clang::LookupResult&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a34430)
#12 0x0000000006a39a16 clang::Sema::ActOnFunctionDeclarator(clang::Scope*, clang::Declarator&, clang::DeclContext*, clang::TypeSourceInfo*, clang::LookupResult&, llvm::MutableArrayRef<clang::TemplateParameterList*>, bool&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a39a16)
#13 0x0000000006a3ec70 clang::Sema::HandleDeclarator(clang::Scope*, clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a3ec70)
#14 0x0000000006a3f620 clang::Sema::ActOnStartOfFunctionDef(clang::Scope*, clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>, clang::SkipBodyInfo*, clang::Sema::FnBodyKind) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6a3f620)
#15 0x000000000667b590 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667b590)
#16 0x00000000066b04fd clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66b04fd)
#17 0x000000000666fb8e clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x666fb8e)
#18 0x000000000667034e clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x667034e)
#19 0x0000000006677ae3 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6677ae3)
#20 0x00000000066789cd clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x66789cd)
#21 0x000000000666aeea clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x666aeea)
#22 0x0000000004526408 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4526408)
#23 0x00000000047e0629 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47e0629)
#24 0x000000000475f1ae clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x475f1ae)
#25 0x00000000048c5dce clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x48c5dce)
#26 0x0000000000cdce6f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcdce6f)
#27 0x0000000000cd4b7a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#28 0x000000000456a119 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#29 0x0000000003afd214 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3afd214)
#30 0x000000000456a70f clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
#31 0x000000000453000d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x453000d)
#32 0x00000000045310fd clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x45310fd)
#33 0x0000000004538a25 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4538a25)
#34 0x0000000000cd9d3f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd9d3f)
#35 0x0000000000ba9264 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba9264)
#36 0x00007ddbe3c29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#37 0x00007ddbe3c29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#38 0x0000000000cd462e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd462e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
ASM generation compiler returned: 134
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkmt9v2zjywP8a5YWQIVGyfjzkwXHi_XY3-21QBwvck0FRI5uNTOpIKnX61x9IybEo22mzF_dwuEW3TaThcOYzw-FIIlGKrTnAtTe98aa3V6TVGyGvX9hXwuMsnl4Vony59vDMw7PHDVNIg9KUKEBMoTVwkERDiYoXRFDVfv8OctIJe8GtF_R_z8W2YTVIdLdraiFBetEMedObjdaN8qKZhxceXqxFWYhaT4Rce3jx3cOLNPrjK_9HEX31prcezn5eHOfD6a3djD-TmpWIihLQN1bXiEqiNkhwNK8JX6OZUiA1Exw9ypY_eXiOmEYKYKuQ3hCNtFGzFqBQQegT0gJRM9CPJqkxqpswCbo_tGn6KzhqJFlvCZJQQsU4rGCnOdkCqoRY0aZBBZGrV3mliWYUMa739z2cGYeim04AdhokPxZAXnqDJOhWchR60Q3y0tuRUUMoS22cKNttc2x896v1zsM35o-JF15IIbSHF3X9vPUbKb4CNb_2cgvGad2WMLgyWz56eHELtJ5svGg2DcLQaHoWJg5WJpp50ewLlEBrIklRgxfNzS8r_dKAF911Agr0g4RnJlpllHk4O8iYZMtNMn1jeoNeryMvuh3OsWg5NcG146e3xoxDwI3LOGSKeNH8_8kWSisV3Xk468KxokRpxzQ86-6bpDDRsfznXjpHvejf1uN70R1T94w_kTX8ZXK2TwCcooqwGspJF5-H-7vZ8g6pttgyjQgq2jWS0AipTW6OFgvTm7aYULHt43ccRqZUC8rDC0R4ifpgIr2BfqGYpNeSUDAro5HQSEFBKSiREq3sLpuRRClBma0KsuVIUckaPTmbdMHEC_IHKdaSbBGR63YLXKs-4URjE6wvHz7sy0efYj7Zh1D5ulu0i4LxQwaa3EX-uvxGZOXHyF8jXxi9xCyahWh10-qJQv7WsEC-v8sSn6itr164JjsvumVcQ438igv_GWQhFJj7yF8i319T6msharohjHvR7Zv2GmHFSaM2QiO_oqIW0i8ZWXOhNKOqm8OSdi570bzHG911wEIDzLkczSIvmmFsoNFWSuAaNUQqkEiLJ-DIw6mX3pi_rQbk4ShAwS7Y_xcVRVhOM2QTo1txL6r74UEyrm3YHrvYZwchSb6thNISyNbDiS2YXNuVYBL2Q4Ln4Ztg15v3WtWN_aFrP6lISE_ZP6-B8Lb5zJdszYkpHS23O16JamFmuYC11hjHWuxYSypaJhmam2B_ASqeQb505v0f4WVtJs16ko7MXHANOz0xJT-aBfb_1ymifoq0LAuIaIynOOhdq1nh4cUuS1ZJ7NeMtzt_zdvuBp0oMUms4XaIY3bs6syTvKKo0RsJpFw9mT30XRPY8c4E07HRcZqgtbIs3mt8nCaO7sTVjbO0ihApTHl8l2Y70NGcHmkOi3frDAtHZ-bqjHLIk_fptEMcnfkw69KsSmj81r57brc8vwufG9HvyR-7rnoHDr0djkKniqVkWsQQnd31TzlBJDH3f7kvnamOL05FS0gUx1Ew9GUJW9LXtA3Qp6GRJ71YUtG3R_OzSI7u3gvx1DZfQLW17mt6IUR9-PfDUfSeOijwCEVOwuQ0ihnVn_kYhZA_RWIonpy415fb44GPLw0s7e77iVfipyAedqY_W23W20xK8vIFKnfdPcK2qYmGByLJFjTIe6b0vkfchyC5TBQMZCcK0SgKQNMzCdltW_8u_o9gdAkwxm8HTDwCUyX4DBibnktNpP5cHbK0-s_xcWZYPrHmRpQvp7P44MWCG6k_GC8vA9jwcwBPHcBJWkxzB_CDbW4HPw_YMs6Oa6ERYnz91oo_0lnuQRo8iAqu9Nuj7jvoCsqZ1q_UL0CsA-IQS1xiRRBX5ZveGRS_SdE2Z0EtG6CnC2OH8LU8HgOxAFjRavM8-T7Qx_Jdpb0XtN_jxnk61LcQ8gvha_jE2cXgW7YO_NSFn1RFBj-E_1kOkvYT1yC7x5P3s_yhxJsBnVHzFG_usYoZIhdAZok4yLLRCg-i-MfI-jbHIXd2uX84uHHe_QpwlosDLh-BS4nb8R6Bu9t1qXW2T7wUrEvgMN4OceBghCPL6dt171E09_AM9fETzOeG_LOFBy3d7fS1UNqN9u5EfXrdJ_8UZVvDp20jpF5qouFCvVrnpsMhHJUgAkCOONjXsdnY9F_T5XcmOTY7XX48xUkcZEOb56KE34DP7FLvLt3tgLYa-kv9a--PtbQ3xLHU6YTjFIIE584zlTR7IS9PmHohIzsbHCNj18hpFRJwcXbTfuJKE07hNNHzXl0kl3s7HUec7i_O6LSkjiO9yQd_nl97g-wtfy9SlHr7HAecZiygJYWkQpSGqy0xOgZvUIcd_IbIfZf52qs71_Dcfjm5jB-dlY4b6ciNuEgJ2sOfh4-2UgycWW5JXf8FVAv5advUJ30aPcgYHX0fOeiwc1RK9gzy-EWnMStzy0ZCwjDvPikd9FZ9g7CSlq29u_-M1r_NoqSuC0KfVhV3C343d59D83AutlvCy_GiPhlDpXs50ZjZiWEw4KMl4-t-G-kC_DpgtaK7nf065kWzgihGV8qK9xQdYXNhpSVhWu1vj9SRujZrQsjBfSMyO5R4m0QdczvEw2lNtkVJPJweUOFs_5b8d1Gcjkc-erdd4jAehOLUG-z-9WPLl6SC-sXB-XboLvC6vrN4mPnuxxGTYmlQof_lFDHQJw2RehK8lQvuV5l4GgVBUJ4FZ2NHjnbMPU2nmI8GGoFzj-RviM6cZmfg28c2ENZtJ6FGrU4UBtW7ufwuCnUeyu-iuGdKO1DeKs2vedAQZlLAfm_6eY59svwSmgaWQzMa0cwInp6z_Hbws9M4nOgYzkXhF9K8QDtr8Tj84tHGnpdRX972HcrefltWZn1R-PG2_eE9ibHMMd3pDYOC5DiJkTH6o-fuVDtzjz8o5mX-zi-sdoijc_wpMYc4QKuVGbZSmki9Gjj307NA7M6SjTu5BAPq9H98zIzy19mHt6MZAimFPfxlr6Oqf8JAtF8R3fkWZI_ywI7p7rRWGMXGzFYB8p-RFkgBIDZo-_vJZss_90fSmOBo701_KArMEjW6RoedrsrrqMyjnFzBdZjiPMzCaRhdba4DGgY5TGNSUoKBJEWep0CLkk4rmlZQXrFrHOA4DMI0TMJwGk6ykBR5mqdJOsXZtAy8OIAtYfXELJ2JkOsre8jmOgxxGqVXNSmgVvbkHcb7WrFn4mHs4bm5Yc-ECO4_d2eB9pfH8qZ1-v7dxAx709sreW3P9xTtWnlxUDOl1cEMzXRtj_wN4zO9_S8-EnXVyvr675956iPyfI3_FQAA__-MCpxs">