clang crashes when using C++ constructs in C code

[berolinux]

Clang (not clang++) crashes on a file that contains just "::", throwing an assertion that such code should be guarded by checking for C++.

Of course this is not valid C, but I'd expect clang to give a proper error instead of an assertion and a backtrace.

$ echo '::' >test.c
$ clang test.c
clang-17: /builddir/build/BUILD/llvm-project-17.0.5.src/clang/lib/Parse/Parser.cpp:2180: bool clang::Parser::TryAnnotateCXXScopeToken(bool): Assertion `getLangOpts().CPlusPlus && "Call sites of this function should be guarded by checking for C++"' 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: /usr/bin/clang-17 -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name output-pstoedit-18c507.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 -fcoverage-compilation-dir=/tmp -resource-dir /usr/lib64/clang/17 -internal-isystem /usr/lib64/clang/17/include -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib64/gcc/x86_64-openmandriva-linux-gnu/13.1.1/../../../../x86_64-openmandriva-linux-gnu/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdebug-compilation-dir=/tmp -ferror-limit 19 -fgnuc-version=13.1.1 -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/test.o -x c test.c
1.      output-pstoedit-18c507.c:1:1: current parser token '::'
 #0 0x00007f514409b796 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/lib64/libLLVM-17.so+0x489b796)
 #1 0x00007f514409a40a llvm::sys::RunSignalHandlers() (/lib64/libLLVM-17.so+0x489a40a)
 #2 0x00007f514409b0b4 (/lib64/libLLVM-17.so+0x489b0b4)
 #3 0x00007f513f2556f0 (/lib64/libc.so.6+0x3d6f0)
 #4 0x00007f513f2a49bc (/lib64/libc.so.6+0x8c9bc)
 #5 0x00007f513f255642 gsignal (/lib64/libc.so.6+0x3d642)
 #6 0x00007f513f23e4ad abort (/lib64/libc.so.6+0x264ad)
 #7 0x00007f513f23e3d5 (/lib64/libc.so.6+0x263d5)
 #8 0x00007f513f24e042 (/lib64/libc.so.6+0x36042)
 #9 0x00007f514a95d8a2 clang::Parser::TryAnnotateCXXScopeToken(bool) (/lib64/libclang-cpp.so.17+0x175d8a2)
#10 0x00007f514a880d4b clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/lib64/libclang-cpp.so.17+0x1680d4b)
#11 0x00007f514a9569ed clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) (/lib64/libclang-cpp.so.17+0x17569ed)
#12 0x00007f514a956874 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/lib64/libclang-cpp.so.17+0x1756874)
#13 0x00007f514a9555b4 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) (/lib64/libclang-cpp.so.17+0x17555b4)
#14 0x00007f514a9533ef clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/lib64/libclang-cpp.so.17+0x17533ef)
#15 0x00007f514a95247e clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) (/lib64/libclang-cpp.so.17+0x175247e)
#16 0x00007f514a85aa16 clang::ParseAST(clang::Sema&, bool, bool) (/lib64/libclang-cpp.so.17+0x165aa16)
#17 0x00007f514cc3a36b clang::FrontendAction::Execute() (/lib64/libclang-cpp.so.17+0x3a3a36b)
#18 0x00007f514cba10b9 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/lib64/libclang-cpp.so.17+0x39a10b9)
#19 0x00007f514ccb4af9 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/lib64/libclang-cpp.so.17+0x3ab4af9)
#20 0x00005642b7f49671 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/bin/clang-17+0x16671)
#21 0x00005642b7f45e50 (/usr/bin/clang-17+0x12e50)
#22 0x00005642b7f446e1 clang_main(int, char**, llvm::ToolContext const&) (/usr/bin/clang-17+0x116e1)
#23 0x00005642b7f54442 main (/usr/bin/clang-17+0x21442)
#24 0x00007f513f23fc0a (/lib64/libc.so.6+0x27c0a)
#25 0x00007f513f23fcc5 __libc_start_main (/lib64/libc.so.6+0x27cc5)
#26 0x00005642b7f41f11 _start (/usr/bin/clang-17+0xef11)
clang: error: unable to execute command: Aborted (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
OpenMandriva 17.0.5-1 clang version 17.0.5 (/builddir/build/BUILD/llvm-project-17.0.5.src/clang 67c77eb4750e684d5c3fa07b1014bf3def1e9277)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/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-a39e9d.c
clang: note: diagnostic msg: /tmp/test-a39e9d.sh
clang: note: diagnostic msg: 

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

The same thing happens in real world code where, for example, a C application tries to #include a header containing C++ constructs, such as

extern void a(const char* b, std::ostream & c, bool d);

int main(void)
{
}

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Bernhard Rosenkraenzer (berolinux)

Clang (not clang++) crashes on a file that contains just "::", throwing an assertion that such code should be guarded by checking for C++.

Of course this is not valid C, but I'd expect clang to give a proper error instead of an assertion and a backtrace.

$ echo '::' >test.c
$ clang test.c
clang-17: /builddir/build/BUILD/llvm-project-17.0.5.src/clang/lib/Parse/Parser.cpp:2180: bool clang::Parser::TryAnnotateCXXScopeToken(bool): Assertion `getLangOpts().CPlusPlus && "Call sites of this function should be guarded by checking for C++"' 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: /usr/bin/clang-17 -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name output-pstoedit-18c507.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 -fcoverage-compilation-dir=/tmp -resource-dir /usr/lib64/clang/17 -internal-isystem /usr/lib64/clang/17/include -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib64/gcc/x86_64-openmandriva-linux-gnu/13.1.1/../../../../x86_64-openmandriva-linux-gnu/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdebug-compilation-dir=/tmp -ferror-limit 19 -fgnuc-version=13.1.1 -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/test.o -x c test.c
1.      output-pstoedit-18c507.c:1:1: current parser token '::'
 #<!-- -->0 0x00007f514409b796 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/lib64/libLLVM-17.so+0x489b796)
 #<!-- -->1 0x00007f514409a40a llvm::sys::RunSignalHandlers() (/lib64/libLLVM-17.so+0x489a40a)
 #<!-- -->2 0x00007f514409b0b4 (/lib64/libLLVM-17.so+0x489b0b4)
 #<!-- -->3 0x00007f513f2556f0 (/lib64/libc.so.6+0x3d6f0)
 #<!-- -->4 0x00007f513f2a49bc (/lib64/libc.so.6+0x8c9bc)
 #<!-- -->5 0x00007f513f255642 gsignal (/lib64/libc.so.6+0x3d642)
 #<!-- -->6 0x00007f513f23e4ad abort (/lib64/libc.so.6+0x264ad)
 #<!-- -->7 0x00007f513f23e3d5 (/lib64/libc.so.6+0x263d5)
 #<!-- -->8 0x00007f513f24e042 (/lib64/libc.so.6+0x36042)
 #<!-- -->9 0x00007f514a95d8a2 clang::Parser::TryAnnotateCXXScopeToken(bool) (/lib64/libclang-cpp.so.17+0x175d8a2)
#<!-- -->10 0x00007f514a880d4b clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&amp;, clang::Parser::ParsedTemplateInfo const&amp;, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/lib64/libclang-cpp.so.17+0x1680d4b)
#<!-- -->11 0x00007f514a9569ed clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec&amp;, clang::AccessSpecifier) (/lib64/libclang-cpp.so.17+0x17569ed)
#<!-- -->12 0x00007f514a956874 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/lib64/libclang-cpp.so.17+0x1756874)
#<!-- -->13 0x00007f514a9555b4 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*) (/lib64/libclang-cpp.so.17+0x17555b4)
#<!-- -->14 0x00007f514a9533ef clang::Parser::ParseTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (/lib64/libclang-cpp.so.17+0x17533ef)
#<!-- -->15 0x00007f514a95247e clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (/lib64/libclang-cpp.so.17+0x175247e)
#<!-- -->16 0x00007f514a85aa16 clang::ParseAST(clang::Sema&amp;, bool, bool) (/lib64/libclang-cpp.so.17+0x165aa16)
#<!-- -->17 0x00007f514cc3a36b clang::FrontendAction::Execute() (/lib64/libclang-cpp.so.17+0x3a3a36b)
#<!-- -->18 0x00007f514cba10b9 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/lib64/libclang-cpp.so.17+0x39a10b9)
#<!-- -->19 0x00007f514ccb4af9 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/lib64/libclang-cpp.so.17+0x3ab4af9)
#<!-- -->20 0x00005642b7f49671 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/usr/bin/clang-17+0x16671)
#<!-- -->21 0x00005642b7f45e50 (/usr/bin/clang-17+0x12e50)
#<!-- -->22 0x00005642b7f446e1 clang_main(int, char**, llvm::ToolContext const&amp;) (/usr/bin/clang-17+0x116e1)
#<!-- -->23 0x00005642b7f54442 main (/usr/bin/clang-17+0x21442)
#<!-- -->24 0x00007f513f23fc0a (/lib64/libc.so.6+0x27c0a)
#<!-- -->25 0x00007f513f23fcc5 __libc_start_main (/lib64/libc.so.6+0x27cc5)
#<!-- -->26 0x00005642b7f41f11 _start (/usr/bin/clang-17+0xef11)
clang: error: unable to execute command: Aborted (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
OpenMandriva 17.0.5-1 clang version 17.0.5 (/builddir/build/BUILD/llvm-project-17.0.5.src/clang 67c77eb4750e684d5c3fa07b1014bf3def1e9277)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/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-a39e9d.c
clang: note: diagnostic msg: /tmp/test-a39e9d.sh
clang: note: diagnostic msg: 

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

The same thing happens in real world code where, for example, a C application tries to #include a header containing C++ constructs, such as

extern void a(const char* b, std::ostream & c, bool d);

int main(void)
{
}

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. In the comments of the issue, request for it to be assigned to you.
2. Fix the issue locally.
3. Run the test suite locally.
   3.1) Remember that the subdirectories under test/ create fine-grained testing targets, so you can
   e.g. use make check-clang-ast to only run Clang's AST tests.
4. Create a Git commit.
5. Run git clang-format HEAD~1 to format your changes.
6. Open a pull request to the upstream repository on GitHub.
   6.1) Detailed instructions can be found here.

If you have any further questions about this issue, don't hesitate to ask via a comment on this Github issue.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Bernhard Rosenkraenzer (berolinux)

Clang (not clang++) crashes on a file that contains just "::", throwing an assertion that such code should be guarded by checking for C++.

Of course this is not valid C, but I'd expect clang to give a proper error instead of an assertion and a backtrace.

$ echo '::' >test.c
$ clang test.c
clang-17: /builddir/build/BUILD/llvm-project-17.0.5.src/clang/lib/Parse/Parser.cpp:2180: bool clang::Parser::TryAnnotateCXXScopeToken(bool): Assertion `getLangOpts().CPlusPlus && "Call sites of this function should be guarded by checking for C++"' 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: /usr/bin/clang-17 -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name output-pstoedit-18c507.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 -fcoverage-compilation-dir=/tmp -resource-dir /usr/lib64/clang/17 -internal-isystem /usr/lib64/clang/17/include -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib64/gcc/x86_64-openmandriva-linux-gnu/13.1.1/../../../../x86_64-openmandriva-linux-gnu/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdebug-compilation-dir=/tmp -ferror-limit 19 -fgnuc-version=13.1.1 -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/test.o -x c test.c
1.      output-pstoedit-18c507.c:1:1: current parser token '::'
 #<!-- -->0 0x00007f514409b796 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/lib64/libLLVM-17.so+0x489b796)
 #<!-- -->1 0x00007f514409a40a llvm::sys::RunSignalHandlers() (/lib64/libLLVM-17.so+0x489a40a)
 #<!-- -->2 0x00007f514409b0b4 (/lib64/libLLVM-17.so+0x489b0b4)
 #<!-- -->3 0x00007f513f2556f0 (/lib64/libc.so.6+0x3d6f0)
 #<!-- -->4 0x00007f513f2a49bc (/lib64/libc.so.6+0x8c9bc)
 #<!-- -->5 0x00007f513f255642 gsignal (/lib64/libc.so.6+0x3d642)
 #<!-- -->6 0x00007f513f23e4ad abort (/lib64/libc.so.6+0x264ad)
 #<!-- -->7 0x00007f513f23e3d5 (/lib64/libc.so.6+0x263d5)
 #<!-- -->8 0x00007f513f24e042 (/lib64/libc.so.6+0x36042)
 #<!-- -->9 0x00007f514a95d8a2 clang::Parser::TryAnnotateCXXScopeToken(bool) (/lib64/libclang-cpp.so.17+0x175d8a2)
#<!-- -->10 0x00007f514a880d4b clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&amp;, clang::Parser::ParsedTemplateInfo const&amp;, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/lib64/libclang-cpp.so.17+0x1680d4b)
#<!-- -->11 0x00007f514a9569ed clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec&amp;, clang::AccessSpecifier) (/lib64/libclang-cpp.so.17+0x17569ed)
#<!-- -->12 0x00007f514a956874 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*, clang::AccessSpecifier) (/lib64/libclang-cpp.so.17+0x1756874)
#<!-- -->13 0x00007f514a9555b4 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&amp;, clang::ParsedAttributes&amp;, clang::ParsingDeclSpec*) (/lib64/libclang-cpp.so.17+0x17555b4)
#<!-- -->14 0x00007f514a9533ef clang::Parser::ParseTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (/lib64/libclang-cpp.so.17+0x17533ef)
#<!-- -->15 0x00007f514a95247e clang::Parser::ParseFirstTopLevelDecl(clang::OpaquePtr&lt;clang::DeclGroupRef&gt;&amp;, clang::Sema::ModuleImportState&amp;) (/lib64/libclang-cpp.so.17+0x175247e)
#<!-- -->16 0x00007f514a85aa16 clang::ParseAST(clang::Sema&amp;, bool, bool) (/lib64/libclang-cpp.so.17+0x165aa16)
#<!-- -->17 0x00007f514cc3a36b clang::FrontendAction::Execute() (/lib64/libclang-cpp.so.17+0x3a3a36b)
#<!-- -->18 0x00007f514cba10b9 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/lib64/libclang-cpp.so.17+0x39a10b9)
#<!-- -->19 0x00007f514ccb4af9 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/lib64/libclang-cpp.so.17+0x3ab4af9)
#<!-- -->20 0x00005642b7f49671 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/usr/bin/clang-17+0x16671)
#<!-- -->21 0x00005642b7f45e50 (/usr/bin/clang-17+0x12e50)
#<!-- -->22 0x00005642b7f446e1 clang_main(int, char**, llvm::ToolContext const&amp;) (/usr/bin/clang-17+0x116e1)
#<!-- -->23 0x00005642b7f54442 main (/usr/bin/clang-17+0x21442)
#<!-- -->24 0x00007f513f23fc0a (/lib64/libc.so.6+0x27c0a)
#<!-- -->25 0x00007f513f23fcc5 __libc_start_main (/lib64/libc.so.6+0x27cc5)
#<!-- -->26 0x00005642b7f41f11 _start (/usr/bin/clang-17+0xef11)
clang: error: unable to execute command: Aborted (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
OpenMandriva 17.0.5-1 clang version 17.0.5 (/builddir/build/BUILD/llvm-project-17.0.5.src/clang 67c77eb4750e684d5c3fa07b1014bf3def1e9277)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/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-a39e9d.c
clang: note: diagnostic msg: /tmp/test-a39e9d.sh
clang: note: diagnostic msg: 

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

The same thing happens in real world code where, for example, a C application tries to #include a header containing C++ constructs, such as

extern void a(const char* b, std::ostream & c, bool d);

int main(void)
{
}

[Lancern]

Hi. I want to help fix this bug. Can someone assign this issue to me? Thanks.

[ChipsSpectre]

@Lancern I hope it is ok for you that I created this pull request, but since the issue is open for more than two weeks I assumed that you are busy in other projects at the moment.

Hi,

I fixed this bug (my first fix for llvm, any suggestions of how to improve my process are welcome).

Line 2705 in ParseDeclCXX.cpp calls TryAnnotateCXXScopeToken() without guarding whether C or C++ is being compiled.
Line 3486 in ParseDecl.cpp has the same issue.

A test file "test.c" which contains only the double colon "::" now yields this error message instead of the exception before.

test.c:1:1: error: expected identifier or '('
1 | ::
| ^
1 error generated.