[clang++] Assertion `NumBits >= MIN_INT_BITS && "bitwidth too small"' failed on valid code

[yijan4845]

This testcase is generated by a fuzzer.

Compiler Explorer: https://godbolt.org/z/nh6G4q779

This valid code will crash on Clang Assertion Trunk, it seems that this goes back to clang 3.1:

typedef struct {
  struct { int a[]; } b;
} S;

void foo() {
  __builtin_va_list list;
__builtin_va_arg(list, S);
}

Stack dump:

clang++: /root/llvm-project/llvm/lib/IR/Type.cpp:276: static llvm::IntegerType* llvm::IntegerType::get(llvm::LLVMContext&, unsigned int): Assertion `NumBits >= MIN_INT_BITS && "bitwidth too small"' 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 -O3 <source>
1.	<eof> parser at end of file
2.	<source>:5:6: LLVM IR generation of declaration 'foo'
3.	<source>:5:6: Generating code for declaration 'foo'
 #0 0x0000000003b9d598 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b9d598)
 #1 0x0000000003b9b25c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b9b25c)
 #2 0x0000000003ae9a68 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007c33daa42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007c33daa969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007c33daa42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007c33daa287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007c33daa2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007c33daa39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000000003567036 llvm::IntegerType::get(llvm::LLVMContext&, unsigned int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3567036)
#10 0x00000000040d37a5 (anonymous namespace)::X86_64ABIInfo::getIndirectResult(clang::QualType, unsigned int) const X86.cpp:0:0
#11 0x00000000040dbbc8 (anonymous namespace)::X86_64ABIInfo::classifyArgumentType(clang::QualType, unsigned int, unsigned int&, unsigned int&, bool, bool) const X86.cpp:0:0
#12 0x00000000040dd969 (anonymous namespace)::X86_64ABIInfo::EmitVAArg(clang::CodeGen::CodeGenFunction&, clang::CodeGen::Address, clang::QualType, clang::CodeGen::AggValueSlot) const X86.cpp:0:0
#13 0x00000000042c9800 clang::CodeGen::CodeGenFunction::EmitVAArg(clang::VAArgExpr*, clang::CodeGen::Address&, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x42c9800)
#14 0x000000000438acf4 (anonymous namespace)::AggExprEmitter::Visit(clang::Expr*) CGExprAgg.cpp:0:0
#15 0x000000000438b590 clang::CodeGen::CodeGenFunction::EmitAggExpr(clang::Expr const*, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x438b590)
#16 0x0000000004352351 clang::CodeGen::CodeGenFunction::EmitAnyExpr(clang::Expr const*, clang::CodeGen::AggValueSlot, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4352351)
#17 0x0000000004378565 clang::CodeGen::CodeGenFunction::EmitIgnoredExpr(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4378565)
#18 0x0000000003efecd5 clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef<clang::Attr const*>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3efecd5)
#19 0x0000000003f069e4 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&, bool, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f069e4)
#20 0x0000000003f6ee84 clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f6ee84)
#21 0x0000000003f80e6c clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f80e6c)
#22 0x0000000003fe981a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fe981a)
#23 0x0000000003fe4535 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fe4535)
#24 0x0000000003fe4aeb clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fe4aeb)
#25 0x0000000003feee63 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#26 0x00000000044f6806 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#27 0x00000000044e73e8 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44e73e8)
#28 0x0000000006620d04 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6620d04)
#29 0x00000000044f4378 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44f4378)
#30 0x00000000047ae299 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47ae299)
#31 0x000000000472cbde clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x472cbde)
#32 0x0000000004893b1e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4893b1e)
#33 0x0000000000cd805f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd805f)
#34 0x0000000000ccfd6a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#35 0x0000000004538049 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
#36 0x0000000003ae9f14 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ae9f14)
#37 0x000000000453863f 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
#38 0x00000000044fdf7d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44fdf7d)
#39 0x00000000044ff06d 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+++0x44ff06d)
#40 0x0000000004506995 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4506995)
#41 0x0000000000cd4f2f clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd4f2f)
#42 0x0000000000ba49e4 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba49e4)
#43 0x00007c33daa29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#44 0x00007c33daa29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#45 0x0000000000ccf81e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xccf81e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[llvmbot]

@llvm/issue-subscribers-clang-codegen

Author: Yihan Yang (yijan4845)

**This testcase is generated by a fuzzer.**

Compiler Explorer: https://godbolt.org/z/nh6G4q779

This valid code will crash on Clang Assertion Trunk, it seems that this goes back to clang 3.1:

typedef struct {
  struct { int a[]; } b;
} S;

void foo() {
  __builtin_va_list list;
__builtin_va_arg(list, S);
}

Stack dump:

clang++: /root/llvm-project/llvm/lib/IR/Type.cpp:276: static llvm::IntegerType* llvm::IntegerType::get(llvm::LLVMContext&, unsigned int): Assertion `NumBits >= MIN_INT_BITS && "bitwidth too small"' 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 -O3 <source>
1.	<eof> parser at end of file
2.	<source>:5:6: LLVM IR generation of declaration 'foo'
3.	<source>:5:6: Generating code for declaration 'foo'
 #<!-- -->0 0x0000000003b9d598 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b9d598)
 #<!-- -->1 0x0000000003b9b25c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3b9b25c)
 #<!-- -->2 0x0000000003ae9a68 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #<!-- -->3 0x00007c33daa42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->4 0x00007c33daa969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #<!-- -->5 0x00007c33daa42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #<!-- -->6 0x00007c33daa287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #<!-- -->7 0x00007c33daa2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #<!-- -->8 0x00007c33daa39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #<!-- -->9 0x0000000003567036 llvm::IntegerType::get(llvm::LLVMContext&amp;, unsigned int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3567036)
#<!-- -->10 0x00000000040d37a5 (anonymous namespace)::X86_64ABIInfo::getIndirectResult(clang::QualType, unsigned int) const X86.cpp:0:0
#<!-- -->11 0x00000000040dbbc8 (anonymous namespace)::X86_64ABIInfo::classifyArgumentType(clang::QualType, unsigned int, unsigned int&amp;, unsigned int&amp;, bool, bool) const X86.cpp:0:0
#<!-- -->12 0x00000000040dd969 (anonymous namespace)::X86_64ABIInfo::EmitVAArg(clang::CodeGen::CodeGenFunction&amp;, clang::CodeGen::Address, clang::QualType, clang::CodeGen::AggValueSlot) const X86.cpp:0:0
#<!-- -->13 0x00000000042c9800 clang::CodeGen::CodeGenFunction::EmitVAArg(clang::VAArgExpr*, clang::CodeGen::Address&amp;, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x42c9800)
#<!-- -->14 0x000000000438acf4 (anonymous namespace)::AggExprEmitter::Visit(clang::Expr*) CGExprAgg.cpp:0:0
#<!-- -->15 0x000000000438b590 clang::CodeGen::CodeGenFunction::EmitAggExpr(clang::Expr const*, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x438b590)
#<!-- -->16 0x0000000004352351 clang::CodeGen::CodeGenFunction::EmitAnyExpr(clang::Expr const*, clang::CodeGen::AggValueSlot, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4352351)
#<!-- -->17 0x0000000004378565 clang::CodeGen::CodeGenFunction::EmitIgnoredExpr(clang::Expr const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4378565)
#<!-- -->18 0x0000000003efecd5 clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef&lt;clang::Attr const*&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3efecd5)
#<!-- -->19 0x0000000003f069e4 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&amp;, bool, clang::CodeGen::AggValueSlot) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f069e4)
#<!-- -->20 0x0000000003f6ee84 clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f6ee84)
#<!-- -->21 0x0000000003f80e6c clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f80e6c)
#<!-- -->22 0x0000000003fe981a clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fe981a)
#<!-- -->23 0x0000000003fe4535 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fe4535)
#<!-- -->24 0x0000000003fe4aeb clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3fe4aeb)
#<!-- -->25 0x0000000003feee63 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#<!-- -->26 0x00000000044f6806 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#<!-- -->27 0x00000000044e73e8 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44e73e8)
#<!-- -->28 0x0000000006620d04 clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6620d04)
#<!-- -->29 0x00000000044f4378 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44f4378)
#<!-- -->30 0x00000000047ae299 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x47ae299)
#<!-- -->31 0x000000000472cbde clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x472cbde)
#<!-- -->32 0x0000000004893b1e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4893b1e)
#<!-- -->33 0x0000000000cd805f cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd805f)
#<!-- -->34 0x0000000000ccfd6a ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->35 0x0000000004538049 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
#<!-- -->36 0x0000000003ae9f14 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ae9f14)
#<!-- -->37 0x000000000453863f 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
#<!-- -->38 0x00000000044fdf7d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x44fdf7d)
#<!-- -->39 0x00000000044ff06d 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+++0x44ff06d)
#<!-- -->40 0x0000000004506995 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+++0x4506995)
#<!-- -->41 0x0000000000cd4f2f clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xcd4f2f)
#<!-- -->42 0x0000000000ba49e4 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xba49e4)
#<!-- -->43 0x00007c33daa29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->44 0x00007c33daa29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->45 0x0000000000ccf81e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xccf81e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134

[shafik]

Maybe related: #48600

[shafik]

@AaronBallman Do you think this should be valid? gcc accepts.

[AaronBallman]

This valid code will crash on Clang Assertion Trunk,

Errr, sort of (no call to __builtin_va_start so that's UB but not pertinent to the crash, and a FAM as the only member of the struct isn't valid C but is a GNU extension we support). Because we support the extension, I think we should accept the code (certainly we shouldn't assert) and it should follow GCC's behavior.