clang: Assertion `NumPositiveBits <= BestWidth && "How could an initializer get larger than ULL?"' failed.

[wierton]

This bug is related to a C23 feature (_BigInt):

enum { B = 66666666666666666666wb };

When compile the above program with clang, clang triggers an assertion failure (Compiler Explorer: https://godbolt.org/z/M6a94abG6):

Diagnostic:

<source>:1:12: warning: '_BitInt' suffix for literals is a C23 extension [-Wc23-extensions]
    1 | enum { B = 66666666666666666666wb };
      |            ^

Assertion:

clang: /root/llvm-project/clang/lib/Sema/SemaDecl.cpp:20114:
void clang::Sema::ActOnEnumBody(clang::SourceLocation, clang::SourceRange, clang::Decl*, llvm::ArrayRef<clang::Decl*>, clang::Scope*, const clang::ParsedAttributesView&):
Assertion `NumPositiveBits <= BestWidth && "How could an initializer get larger than ULL?"' failed.

Backtrace:

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 -S --gcc-toolchain=/opt/compiler-explorer/gcc-9.2.0 -fcolor-diagnostics -fno-crash-diagnostics -O0 <source>
1.	<source>:1:36: current parser token ';'
 #0 0x000000000372dc98 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x372dc98)
 #1 0x000000000372b95c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x372b95c)
 #2 0x0000000003674298 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007f6d0d86d420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #4 0x00007f6d0d33000b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #5 0x00007f6d0d30f859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #6 0x00007f6d0d30f729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #7 0x00007f6d0d320fd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #8 0x00000000061f574e clang::Sema::ActOnEnumBody(clang::SourceLocation, clang::SourceRange, clang::Decl*, llvm::ArrayRef<clang::Decl*>, clang::Scope*, clang::ParsedAttributesView const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x61f574e)
 #9 0x0000000005ed549b clang::Parser::ParseEnumBody(clang::SourceLocation, clang::Decl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ed549b)
#10 0x0000000005edd490 clang::Parser::ParseEnumSpecifier(clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5edd490)
#11 0x0000000005ed9393 clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ed9393)
#12 0x0000000005ea4224 clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ea4224)
#13 0x0000000005ea4b5f clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (.part.0) Parser.cpp:0:0
#14 0x0000000005eac504 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5eac504)
#15 0x0000000005eacd2d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5eacd2d)
#16 0x0000000005ead170 clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ead170)
#17 0x0000000005e9fda2 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5e9fda2)
#18 0x0000000004999d08 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4999d08)
#19 0x00000000041fd819 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x41fd819)
#20 0x000000000417ecbe clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x417ecbe)
#21 0x00000000042dc99e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x42dc99e)
#22 0x0000000000befa36 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbefa36)
#23 0x0000000000be72fa ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#24 0x0000000003fdaea9 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
#25 0x0000000003674744 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3674744)
#26 0x0000000003fdb49f 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
#27 0x0000000003fa3665 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fa3665)
#28 0x0000000003fa40cd 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+0x3fa40cd)
#29 0x0000000003fabff5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fabff5)
#30 0x0000000000becedc clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbecedc)
#31 0x0000000000ae7071 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xae7071)
#32 0x00007f6d0d311083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#33 0x0000000000be6dde _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbe6dde)
clang: error: clang frontend command failed with exit code 134 (use -v to see invocation)

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: wt.cc (wierton)

This bug is related to a C23 feature (_BigInt): ``` enum { B = 66666666666666666666wb }; ```

When compile the above program with clang, clang triggers an assertion failure (Compiler Explorer: https://godbolt.org/z/M6a94abG6):

<source>:1:12: warning: '_BitInt' suffix for literals is a C23 extension [-Wc23-extensions]
    1 | enum { B = 66666666666666666666wb };
      |            ^
clang: /root/llvm-project/clang/lib/Sema/SemaDecl.cpp:20114: void clang::Sema::ActOnEnumBody(clang::SourceLocation, clang::SourceRange, clang::Decl*, llvm::ArrayRef<clang::Decl*>, clang::Scope*, const clang::ParsedAttributesView&): Assertion `NumPositiveBits <= BestWidth && "How could an initializer get larger than ULL?"' 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 -S --gcc-toolchain=/opt/compiler-explorer/gcc-9.2.0 -fcolor-diagnostics -fno-crash-diagnostics -O0 <source>
1.	<source>:1:36: current parser token ';'
 #<!-- -->0 0x000000000372dc98 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x372dc98)
 #<!-- -->1 0x000000000372b95c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x372b95c)
 #<!-- -->2 0x0000000003674298 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #<!-- -->3 0x00007f6d0d86d420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #<!-- -->4 0x00007f6d0d33000b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #<!-- -->5 0x00007f6d0d30f859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #<!-- -->6 0x00007f6d0d30f729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #<!-- -->7 0x00007f6d0d320fd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #<!-- -->8 0x00000000061f574e clang::Sema::ActOnEnumBody(clang::SourceLocation, clang::SourceRange, clang::Decl*, llvm::ArrayRef&lt;clang::Decl*&gt;, clang::Scope*, clang::ParsedAttributesView const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x61f574e)
 #<!-- -->9 0x0000000005ed549b clang::Parser::ParseEnumBody(clang::SourceLocation, clang::Decl*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ed549b)
#<!-- -->10 0x0000000005edd490 clang::Parser::ParseEnumSpecifier(clang::SourceLocation, clang::DeclSpec&amp;, clang::Parser::ParsedTemplateInfo const&amp;, clang::AccessSpecifier, clang::Parser::DeclSpecContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5edd490)
#<!-- -->11 0x0000000005ed9393 clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&amp;, clang::Parser::ParsedTemplateInfo const&amp;, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ed9393)
#<!-- -->12 0x0000000005ea4224 clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec&amp;, clang::AccessSpecifier) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ea4224)
#<!-- -->13 0x0000000005ea4b5f clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*, clang::AccessSpecifier) (.part.0) Parser.cpp:0:0
#<!-- -->14 0x0000000005eac504 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5eac504)
#<!-- -->15 0x0000000005eacd2d clang::Parser::ParseTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5eacd2d)
#<!-- -->16 0x0000000005ead170 clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ead170)
#<!-- -->17 0x0000000005e9fda2 clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5e9fda2)
#<!-- -->18 0x0000000004999d08 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4999d08)
#<!-- -->19 0x00000000041fd819 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x41fd819)
#<!-- -->20 0x000000000417ecbe clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x417ecbe)
#<!-- -->21 0x00000000042dc99e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x42dc99e)
#<!-- -->22 0x0000000000befa36 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbefa36)
#<!-- -->23 0x0000000000be72fa ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->24 0x0000000003fdaea9 void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const::'lambda'()&gt;(long) Job.cpp:0:0
#<!-- -->25 0x0000000003674744 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3674744)
#<!-- -->26 0x0000000003fdb49f clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const (.part.0) Job.cpp:0:0
#<!-- -->27 0x0000000003fa3665 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fa3665)
#<!-- -->28 0x0000000003fa40cd clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fa40cd)
#<!-- -->29 0x0000000003fabff5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fabff5)
#<!-- -->30 0x0000000000becedc clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbecedc)
#<!-- -->31 0x0000000000ae7071 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xae7071)
#<!-- -->32 0x00007f6d0d311083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#<!-- -->33 0x0000000000be6dde _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbe6dde)
clang: error: clang frontend command failed with exit code 134 (use -v to see invocation)

[shafik]

Confirmed CC @AaronBallman

[AaronBallman]

C23 6.7.2.2p4: For an enumeration without a fixed underlying type, the expression that defines the value of an enumeration constant shall be an integer constant expression. For all the integer constant expressions which make up the values of the enumeration constants, there shall be a type capable of representing all the values that is a standard or extended signed or unsigned integer type, or char.

_BitInt is not a standard or extended signed or unsigned integer type, it's a bit-precise integer type. So this code should be rejected.

Note, we should still accept:

enum E {
  Foo = 1wb
};

because 6.7.2.2p12: "... int, if given explicitly with = and the value of the integer constant expression is representable by an int; or,"
but we don't yet implement N3029.