clang 15 segfault on malformed cpp file

[notnoop]

Clang 15 segfaults when compiling a() { if constexpr (__adl_swap<> . This is a regression - Clang 14 reports errors and exits cleanly (with exit code 1).

Here is my compiler output along with diagnostic file.

$ cat test.cpp
a() { if constexpr (__adl_swap<>
$ /usr/lib/llvm-15/bin/clang --version
Ubuntu clang version 15.0.7
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-15/bin
$ /usr/lib/llvm-15/bin/clang ./test.cpp
./test.cpp:1:1: error: a type specifier is required for all declarations
a() { if constexpr (__adl_swap<>
^
./test.cpp:1:10: warning: constexpr if is a C++17 extension [-Wc++17-extensions]
a() { if constexpr (__adl_swap<>
         ^
./test.cpp:1:21: error: use of undeclared identifier '__adl_swap'; did you mean '__sync_swap'?
a() { if constexpr (__adl_swap<>
                    ^~~~~~~~~~                                                                                                                                                                                                                                                                                          __sync_swap
./test.cpp:1:21: note: '__sync_swap' declared here
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-15/bin/clang -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all --mrelax-relocations -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name test.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mfra
me-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=gdb -fcoverage-compilation-dir=/tmp/repro/gg/creduce -resource-dir /usr/lib/llvm-15/lib/
clang/15.0.7 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/x86_64-linux-gnu/c++/11 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/backward -internal-isystem /
usr/lib/llvm-15/lib/clang/15.0.7/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/incl
ude -fdeprecated-macro -fdebug-compilation-dir=/tmp/repro/gg/creduce -ferror-limit 19 -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/test-a77114.o -x c++ ./test.cpp
1.      <eof> parser at end of file
2.      ./test.cpp:1:5: parsing function body 'a'
3.      ./test.cpp:1:5: in compound statement ('{}')
 #0 0x00007f13fa891e91 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/llvm-15/bin/../lib/libLLVM-15.so.1+0xf01e91)
 #1 0x00007f13fa88fbde llvm::sys::RunSignalHandlers() (/usr/lib/llvm-15/bin/../lib/libLLVM-15.so.1+0xeffbde)
 #2 0x00007f13fa8923bb (/usr/lib/llvm-15/bin/../lib/libLLVM-15.so.1+0xf023bb)
 #3 0x00007f14043af940 __restore_rt (/lib/libc6-prof/x86_64-linux-gnu/libpthread.so.0+0x14940)
 #4 0x00007f13f95a7265 /build/glibc-SzIz7B/glibc-2.31/string/../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:436:0
 #5 0x00007f140169bf67 clang::Expr::EvaluateKnownConstInt(clang::ASTContext const&, llvm::SmallVectorImpl<std::pair<clang::SourceLocation, clang::PartialDiagnostic>>*) const (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xd79f67)
 #6 0x00007f1401dbc5b7 clang::Sema::ActOnCondition(clang::Scope*, clang::SourceLocation, clang::Expr*, clang::Sema::ConditionKind, bool) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0x149a5b7)
 #7 0x00007f140140bf05 clang::Parser::ParseCXXCondition(clang::ActionResult<clang::Stmt*, true>*, clang::SourceLocation, clang::Sema::ConditionKind, bool, clang::Parser::ForRangeInfo*, bool) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xae9f05)
 #8 0x00007f1401459314 clang::Parser::ParseParenExprOrCondition(clang::ActionResult<clang::Stmt*, true>*, clang::Sema::ConditionResult&, clang::SourceLocation, clang::Sema::ConditionKind, bool, clang::SourceLocation*, clang::SourceLocation*) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0x
b37314)
 #9 0x00007f14014537e3 clang::Parser::ParseIfStatement(clang::SourceLocation*) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb317e3)
#10 0x00007f1401451069 clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::ParsedAttributes&, clang::ParsedAttributes&) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb2f069)
#11 0x00007f140144fe3f clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb2de3f)
#12 0x00007f1401458b10 clang::Parser::ParseCompoundStatementBody(bool) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb36b10)
#13 0x00007f1401459b45 clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb37b45)
#14 0x00007f1401473e12 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb51e12)
#15 0x00007f14013c87b8 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xaa67b8)
#16 0x00007f1401472e3a clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb50e3a)
#17 0x00007f1401472897 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb50897)
#18 0x00007f1401471bba clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb4fbba)
#19 0x00007f140146fe83 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb4de83)
#20 0x00007f140146f94f clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xb4d94f)
#21 0x00007f14013ae7a6 clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0xa8c7a6)
#22 0x00007f140259f9f5 clang::CodeGenAction::ExecuteAction() (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0x1c7d9f5)
#23 0x00007f1402fd3bd7 clang::FrontendAction::Execute() (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0x26b1bd7)
#24 0x00007f1402f47bc6 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0x2625bc6)
#25 0x00007f14030515da clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/llvm-15/bin/../lib/libclang-cpp.so.15+0x272f5da)
#26 0x000055e2be54291f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/lib/llvm-15/bin/clang+0x1391f)
#27 0x000055e2be540b1b (/usr/lib/llvm-15/bin/clang+0x11b1b)
#28 0x000055e2be54096c clang_main(int, char**) (/usr/lib/llvm-15/bin/clang+0x1196c)
#29 0x00007f13f94380db __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:342:3
#30 0x000055e2be53d32e _start (/usr/lib/llvm-15/bin/clang+0xe32e)
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 15.0.7
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-15/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/test-bf5a61.cpp
clang: note: diagnostic msg: /tmp/test-bf5a61.sh
clang: note: diagnostic msg:

********************

/tmp/test-bf5a61.cpp content:

# 1 "<built-in>"
# 1 "./test.cpp"
a() { if constexpr (__adl_swap<>

/tmp/test-bf5a61.sh content:

# Crash reproducer for Ubuntu clang version 15.0.7
# Driver args: "./test.cpp"
# Original command:  "/usr/lib/llvm-15/bin/clang" "-cc1" "-triple" "x86_64-pc-linux-gnu" "-emit-obj" "-mrelax-all" "--mrelax-relocations" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "test.cpp" "-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" "-mllvm" "-treat-scalable-fixed-error-as-warning" "-debugger-tuning=gdb" "-fcoverage-compilation-dir=/tmp/repro/gg/creduce" "-resource-dir" "/usr/lib/llvm-15/lib/clang/15.0.7" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/x86_64-linux-gnu/c++/11" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/backward" "-internal-isystem" "/usr/lib/llvm-15/lib/clang/15.0.7/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" "-fdeprecated-macro" "-fdebug-compilation-dir=/tmp/repro/gg/creduce" "-ferror-limit" "19" "-fgnuc-version=4.2.1" "-fcxx-exceptions" "-fexceptions" "-fcolor-diagnostics" "-faddrsig" "-D__GCC_HAVE_DWARF2_CFI_ASM=1" "-o" "/tmp/test-a77114.o" "-x" "c++" "./test.cpp"
 "/usr/lib/llvm-15/bin/clang" "-cc1" "-triple" "x86_64-pc-linux-gnu" "-emit-obj" "-mrelax-all" "--mrelax-relocations" "-disable-free" "-clear-ast-before-backend" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "test.cpp" "-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" "-mllvm" "-treat-scalable-fixed-error-as-warning" "-debugger-tuning=gdb" "-fcoverage-compilation-dir=/tmp/repro/gg/creduce" "-fdeprecated-macro" "-fdebug-compilation-dir=/tmp/repro/gg/creduce" "-ferror-limit" "19" "-fgnuc-version=4.2.1" "-fcxx-exceptions" "-fexceptions" "-fcolor-diagnostics" "-faddrsig" "-D__GCC_HAVE_DWARF2_CFI_ASM=1" "-x" "c++" "test-bf5a61.cpp"

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[EugeneZelenko]

Could you please try 16 or main branch? https://godbolt.org should be helpful.

[tbaederr]

Just checked, also happens in main.

[shafik]

Looks like a duplicate of: #53345 maybe we fixed it an broke it again or maybe the problem existing in several places. but we definitely should never crash: https://godbolt.org/z/f9MMYzT4o

Assertion:

clang++: /root/llvm-project/clang/lib/AST/ExprConstant.cpp:15492:
llvm::APSInt clang::Expr::EvaluateKnownConstInt(const clang::ASTContext&, llvm::SmallVectorImpl<std::pair<clang::SourceLocation, clang::PartialDiagnostic> >*) const:
Assertion `Result && "Could not evaluate expression"' failed.

[Fznamznon]

After spending some time on this, I'm not sure this ever worked. I built 12.0.1 locally and it asserts the same way. I think the problem is the poor check that we actually can evaluate constexpr if condition before evaluating it. In most cases the evaluation is never reached, but in case there was a typo and <> following it (making clang thinkinf that was probably a template id, and therefore handled differently), we end up with "valid" expression for condition after typo correction which is though still can't be evaluated. #53345 is the same issue. Proposed fix https://reviews.llvm.org/D148206 .