<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/115490>115490</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang-20 crashed with no_caller_saved_registers attribute. Assertion `At && "Received null Attr object!"' failed.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

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

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

<pre>
    clang-20 crashed with ```no_caller_saved_registers``` attribute .

Compiler explorer: https://godbolt.org/z/bKoP3zT4j

```
$cat mutant.c
int a();
int __attribute__((no_caller_saved_registers)) b();
__typeof(b) a;

Reduced by Creduce.
Also crashed on clang-19.

$clang-19 mutant.c
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: /usr/lib/llvm-19/bin/clang -cc1 -triple x86_64-pc-linux-gnu -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name mutant.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/home/code/reduce -fcoverage-compilation-dir=/home/code/reduce -resource-dir /usr/lib/llvm-19/lib/clang/19 -internal-isystem /usr/lib/llvm-19/lib/clang/19/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -ferror-limit 19 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/mutant-bb858a.o -x c mutant.c
1.      mutant.c:3:14: current parser token ';'
 #0 0x00007fa81efce246 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/llvm-19/bin/../lib/libLLVM.so.19.0+0xea7246)
 #1 0x00007fa81efcbe20 llvm::sys::RunSignalHandlers() (/usr/lib/llvm-19/bin/../lib/libLLVM.so.19.0+0xea4e20)
 #2 0x00007fa81efce90b (/usr/lib/llvm-19/bin/../lib/libLLVM.so.19.0+0xea790b)
 #3 0x00007fa81dc06520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007fa826b720d1 clang::Attr::getSpelling() const (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xeb90d1)
 #5 0x00007fa826a299c8 clang::FormatASTNodeDiagnosticArgument(clang::DiagnosticsEngine::ArgumentKind, long, llvm::StringRef, llvm::StringRef, llvm::ArrayRef<std::pair<clang::DiagnosticsEngine::ArgumentKind, long>>, llvm::SmallVectorImpl<char>&, void*, llvm::ArrayRef<long>) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xd709c8)
 #6 0x00007fa826766752 clang::Diagnostic::FormatDiagnostic(char const*, char const*, llvm::SmallVectorImpl<char>&) const (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xaad752)
 #7 0x00007fa8289cf44c clang::TextDiagnosticPrinter::HandleDiagnostic(clang::DiagnosticsEngine::Level, clang::Diagnostic const&) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x2d1644c)
 #8 0x00007fa82676c3f4 clang::DiagnosticIDs::ProcessDiag(clang::DiagnosticsEngine&) const (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xab33f4)
 #9 0x00007fa8267660b2 clang::DiagnosticsEngine::EmitCurrentDiagnostic(bool) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xaad0b2)
#10 0x00007fa82722080e clang::Sema::EmitCurrentDiagnostic(unsigned int) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x156780e)
#11 0x00007fa8272abfb9 clang::SemaBase::ImmediateDiagBuilder::~ImmediateDiagBuilder() (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x15f2fb9)
#12 0x00007fa82722133b clang::SemaBase::SemaDiagnosticBuilder::~SemaDiagnosticBuilder() (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x156833b)
#13 0x00007fa8273b01c8 clang::Sema::MergeFunctionDecl(clang::FunctionDecl*, clang::NamedDecl*&, clang::Scope*, bool, bool) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x16f71c8)
#14 0x00007fa8273cc8c3 clang::Sema::CheckFunctionDeclaration(clang::Scope*, clang::FunctionDecl*, clang::LookupResult&, bool, bool) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x17138c3)
#15 0x00007fa8273bf8eb clang::Sema::ActOnFunctionDeclarator(clang::Scope*, clang::Declarator&, clang::DeclContext*, clang::TypeSourceInfo*, clang::LookupResult&, llvm::MutableArrayRef<clang::TemplateParameterList*>, bool&) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x17068eb)
#16 0x00007fa8273bb438 clang::Sema::HandleDeclarator(clang::Scope*, clang::Declarator&, llvm::MutableArrayRef<clang::TemplateParameterList*>) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x1702438)
#17 0x00007fa8273ba918 clang::Sema::ActOnDeclarator(clang::Scope*, clang::Declarator&) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x1701918)
#18 0x00007fa826901390 clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xc48390)
#19 0x00007fa8268ff0e6 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xc460e6)
#20 0x00007fa8269bd987 clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xd04987)
#21 0x00007fa8269bd33b clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xd0433b)
#22 0x00007fa8269bc547 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xd03547)
#23 0x00007fa8269baa27 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xd01a27)
#24 0x00007fa8268e87de clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0xc2f7de)
#25 0x00007fa82897b0b5 clang::FrontendAction::Execute() (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x2cc20b5)
#26 0x00007fa8288eb2f4 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x2c322f4)
#27 0x00007fa8289f7dee clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/llvm-19/bin/../lib/libclang-cpp.so.19.0+0x2d3edee)
#28 0x0000560b7f6f1bc5 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/lib/llvm-19/bin/clang+0x11bc5)
#29 0x0000560b7f6eead5 (/usr/lib/llvm-19/bin/clang+0xead5)
#30 0x0000560b7f6edc9b clang_main(int, char**, llvm::ToolContext const&) (/usr/lib/llvm-19/bin/clang+0xdc9b)
#31 0x0000560b7f6fbf36 main (/usr/lib/llvm-19/bin/clang+0x1bf36)
#32 0x00007fa81dbedd90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#33 0x00007fa81dbede40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#34 0x0000560b7f6ec765 _start (/usr/lib/llvm-19/bin/clang+0xc765)
clang: error: unable to execute command: Segmentation fault (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
Ubuntu clang version 19.0.0 (++20240722031324+65825cd5431c-1~exp1~20240722151445.1819)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-19/bin
clang: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg: /tmp/mutant-c62a1c.c
clang: note: diagnostic msg: /tmp/mutant-c62a1c.sh
clang: note: diagnostic msg: 

********************
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJy8WktT4zjX_jVmo1LKlh1fFiwCId3U0NMUYWaWKVk6Npq2JX-yTMMs5rd_Jdu5yAQaetIvRUEiyUfPeXRukkXbVpQS4NybX3jz5RntzIPS54LWVCr5XKuuZe1ZrvjzOauoLDHxEdO0fQCOvgvzgLzYH36l2jBaVaA3LX0EvtFQitaAbncjEDVGi7wzgGaev_T8xfD3UtWNqEAjeGoqpUF74QI9GNO0XrjwyMojq1LxXFVmpnTpkdU_Hlnlv6nb8J_76O9DSbupxq8kYtSgujNUmhkbGoU0iHok9UjmhRf7ts1mB2-z6fvT11UimUcylE_EbDbmuQFVeCTNbT_d9Qx_74B3DDjKn9Gl7j-PPCyqVu1oVRINVAeZQ5PVZmyfqHR7c7VYX6G2y2thEEV5VyINjdIGGTVlUpiHLp8xVXtkVVWP23-40epvYMYjK9G2HbQeWSEqORKSVR0HZB5ggIhyyr4ZTRl45BI1GhqtGLQtcNSqTg_N9knatooJaoAj3UnUMi0aM6q0NpR9Q7yrG4usb_Jn6FarUtMaUV12NUhjYSOPrLpWW5gi34INMmsCQnpk1XOCMGMBwkaLpgL0lMabOMINw5WQ3RMuZYcw1MJglf-NsJ2VC40oRpiLluYV4EIDIMwqoBrT1uAcCqUBW1VB8v24fvZH0KIQoPtmRjXHj7TqAEtaQ4twTYXEhaiGht1aIVxrqBSjRiiJa8WhQo1gCDeC4QoeoUJk-CJa3AhAuC40rQE3SkhjvWJJqwrhoqbmAYPWUiFcFA1mStrlMF64VBLhQiqsVSe5kCW2YxGumZKt0R0zSmNaCdpanEUnvwvJsbGatV64JAgbqkswmDWdZRHHEcKmk9A3lCBBW8Ac8q4sQdsuIUsvXJY8R7jo2zHr3XnQkgsL2yOrB1WDXSzF7b_B-BEumHoETUv4yEMaBjOz4143juF7bxweWQUZwj2JklZYtM-tgfr9z1qfGL3gLSmK0eqdQ_sJSsY8shqNdWepdsbAI6vZ7OWfI2NfzgZP9gN7Oes49Iict5_--BQIF6C10rgSNiJZ9otSdsx6TiuU9MJlNCOzAOGi_SYarLjG7AHYNywkLuuit4xKacwFLaVqjWDWXinnuhUlwsvN5tPl5ebz4s-rzfKvxd2KbC5X15vF-osXLgOElUVk6sYjq8H7cJ6n85TOFMJPiE3CZzBD_c-uNVyEXrgIIht9WKc1SIMaqlvQyKhvIJFHEhvaSTIIQB4JfeQ_-b7vJwVNAygYkChGfXwNF164aJ_b4cOtFtL00e9-CKHpfpCm3zeqNRpo7ZHYhlEhjU0kfZ55Mwr25jF2ifzm5s8vs1bNgmzme-TCfwKakCi2uWoHOJgAzoH4xwDfdXItSkmrz1Tyqk9-6YkwRUB8BxOZkpj5-UmUz_zcmSg8nIgzP54Tf5xokHPE0yqRMys37oVGZD4BHx3IJHGeEJ8HQyYfiFwYo4dPJZh1A1VlY-dAZh-fP6zpUA6wpnHVzTOfBw60uQONkixj6SG0ldI1NYv1_e-Kw3Lnc4sxDXskPRi872-vZCkkjOqNg38TklvTrZTV7vLApNZGC1neQfGu5oXW9Nm2hpet4UNbQ21quPxJMOGV_XXnrmlV_Qk2L17XTWVlP1DdD-v971EJ7pHFq8i2cn_CH44vHk_8jKXO4sXO4iVxnMwJOkrB4WIetJLUKjXY2KjMi4b3UnJaU6WUJ3PiaJscaptmrIgidqjtPTwd6NZHUxjdaghQruI_tJQbW3j1lBwbuuUoPt0KEx7EUcQcpdPJErOwiI4Dul7u8khfdNueH-n5C9YtD8MiclTIplbq569YqUP_VS3M5ZBinYXLlapOxzml3M_3dmaz32G-JgkhfurDId411PRtiJ3st878Z5P0cajBPE5SHxysgYuV5kWeTbFe0Hak9Lqugdttl0V70YmKbx3k36NdP5fOX0NfkCLPHPRkwnQQhvnr6O23Pc0u_ON9p8Ufp2GYO_hDB3-Y-4GbPPeW8gV0CatOMruNWQKrXM90exaToPM7rYHvuuJJ75qpBsaHBt_Y_j-Z6nGRBAepx6oeuaozlrLwuOqXtno_VJDqfjPnMnCoxbuJuVHqW9fcQdtVZiTmFzGQBGHKQoeB-WTxixReGO9YFTDzVU4ZUPpdBBwOn6687btU0sCTefng_XMD6343fC0L9S7u9pn-S9fv_A_KGSfP1k1FDdxSTWswoG_EUCwMJdTA_AnTYpD4cQqu58UT8vMofMXzxtT_H1k_BTUn5INEoeuOyYQPmgWv8NEb43-j44SKBFngKuLWO5kfhJl_COW232wffD6IKIvCgN5jXUi-2J7btpNK6A2vejED366qdaSDsu_Vp1ZK31FZwrUUg2OeijAWpWHmO3y5xVVaFD7EP-Trk1Zd4zJi-4Qsbe-6AXY82AyU7ULOSwIcwj9G7JHE1kevm_FY9KVV_o8oj32IDyknvmuiOc_S5IeUf9X7BFBcj6dlL5fgHQz-cMSby7hgdm9g-_pz6hNuT_0oSxOHqGBK1KS8e8uXHb6EFC8rhl9C19TGfiVdk2qSkAldbB69bVdXT4MZvVpU_SqKTkdCOI9cmwknJFBK3ibhXjX9Rv1lUf21of_Xwa2ZngttA2Cfva-OxJ191a54V8F13Sht1oYaOGn6435Aiau9e1CYQppweKH9Yn0_ydoW8K8sfxkpEu5sPMncPYxJcj-fO4W7tllC8kXvw-N2-QlYZ0k84baMMEb8fO5gc4rDNIWcuGcm27fK17I1VDJw0I2A3e2Zq8xJz3xYSMjBgYnFPznostw7VjAi3avxuMuR6VtqntJ1CQ-Bg2sT29ptHvt5UsRFkLM5YizY1NTKTY-ek7rnjcMW4sUZ5O6w9T3wx7dztsC0CByImQsRgPL5h0TaBw4l7t7ubCVylo1Jbqt2fwg0KNXrMDlVvVdqu4v74JniHpWd1EEVTJYiL8IYWTwf488-5sh1XsPwHDjPPvh2hGTcLWEnb1xy4BD5aLOxj21aQ7XZHAB_9ywQubNEk3ViSTxHg_wPcWKf2wneehvq32naD520u0NkFILBSxFTdU0lt51rKGuQpvdVVNCu6qdmSkN_3wH4G4KHywzFGIm2UlFBRQUc8a6fs-1fx1mhXQsIP_ZtAEgchIhxhj_yTppuFDu-fEXWvWfjgl545IL4JPITQvwwCEnkkYt4npI54_MoDBgO_oWnJvh3OyiYB1E0nwVpsD_lu-8vDVj8R25ejEMeNFCO-lsPdmCjWvE0dPWRq6qAL4X-4X0PlzepjI3raP-aGNVt37M1if_we3D1Zrxgs7i_X1x-Rvefr9Dq683N17-uf_-EVtc3V2t0_7VvvvjjE7q7uv16d7-71nJ77IJM2vb3g167JLMboAH1N0aAI2p2It-j_-T9N4sJDdj2jffPC2gfProEp1qI7dWuM34e8izM6BmcB0kY-EmcpuTs4TxlQUyKKKU-jcEPGYmjKE78iARRXiSsOBPn1oiDwE-DKAoImSUsT_w09wmN52kAzIt8qKmoZtbmZkqXZ_1VqPMgmEeZf1bRHKq2vylHiITvqO_1CPHmyzN93htq3pWtF_mVaE27F2OEqeCVC3SvXjLbX5eboUXbgu4Dihf7CxtQYo_EyCPkDhiIR-BIdlWFbI2PVD5c5AosNJKM0WN21unq_Ocvg40kPJ6T_w8AAP__IK0kkw">