[llvm-bugs] [Bug 52300] New: Crash on (rather ridiculous) pointer declaration

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52300

            Bug ID: 52300
           Summary: Crash on (rather ridiculous) pointer declaration
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C
          Assignee: unassignedclangbugs at nondot.org
          Reporter: gabravier at gmail.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

#define PTR1 * * * * * * * * * *
#define PTR2 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1 PTR1
#define PTR3 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2 PTR2
#define PTR4 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3 PTR3
#define PTR5 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4 PTR4
#define PTR6 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5 PTR5

int PTR4  q3_var = 0;

Trying to compile this crashes Clang, with this message:

Stack dump:
0.      Program arguments: /usr/bin/clang-12 -cc1 -triple
x86_64-unknown-linux-gnu -emit-obj -mrelax-all --mrelax-relocations
-disable-free -disable-llvm-verifier -discard-value-names -main-file-name
test.c -mrelocation-model static -mframe-pointer=all -fmath-errno
-fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64
-tune-cpu generic -fno-split-dwarf-inlining -debugger-tuning=gdb -resource-dir
/usr/lib64/clang/12.0.1 -internal-isystem /usr/local/include -internal-isystem
/usr/lib64/clang/12.0.1/include -internal-externc-isystem /include
-internal-externc-isystem /usr/include -fdebug-compilation-dir
/tmp/tmp.621xf1iUgA -ferror-limit 19 -fgnuc-version=4.2.1 -fcolor-diagnostics
-faddrsig -o /tmp/test-5d4390.o -x c test.c
1.      test.c:8:5 <Spelling=test.c:1:28>: current parser token '*'
  #0 0x00007fa9c0d183f6 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int)
(/lib64/libLLVM-12.so+0xc063f6)
  #1 0x00007fa9c0d162e4 llvm::sys::RunSignalHandlers()
(/lib64/libLLVM-12.so+0xc042e4)
  #2 0x00007fa9c0d16466 (/lib64/libLLVM-12.so+0xc04466)
  #3 0x00007fa9bfd61320 __restore_rt
/usr/src/debug/glibc-2.33-20.fc34.x86_64/signal/../sysdeps/unix/sysv/linux/sigaction.c:675:0
  #4 0x00007fa9c6d1622b clang::DeclSpec::Finish(clang::Sema&,
clang::PrintingPolicy const&) (/lib64/libclang-cpp.so.12+0x103c22b)
  #5 0x00007fa9c6703a47
clang::Parser::ParseTypeQualifierListOpt(clang::DeclSpec&, unsigned int, bool,
bool, llvm::Optional<llvm::function_ref<void ()> >)
(/lib64/libclang-cpp.so.12+0xa29a47)
  #6 0x00007fa9c66fe2a9
clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void
(clang::Parser::*)(clang::Declarator&)) (/lib64/libclang-cpp.so.12+0xa242a9)
  #7 0x00007fa9c66fe2e1
clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void
(clang::Parser::*)(clang::Declarator&)) (/lib64/libclang-cpp.so.12+0xa242e1)
  #8 0x00007fa9c66fe2e1
clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void
(clang::Parser::*)(clang::Declarator&)) (/lib64/libclang-cpp.so.12+0xa242e1)
  #9 0x00007fa9c66fe2e1 
[most of this stack dump omitted because I don't exactly wan
clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void
(clang::Parser::*)(clang::Declarator&)) (/lib64/libclang-cpp.so.12+0xa242e1)
#253 0x00007fa9c66fe2e1
clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void
(clang::Parser::*)(clang::Declarator&)) (/lib64/libclang-cpp.so.12+0xa242e1)
#254 0x00007fa9c66fe2e1
clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void
(clang::Parser::*)(clang::Declarator&)) (/lib64/libclang-cpp.so.12+0xa242e1)
#255 0x00007fa9c66fe2e1
clang::Parser::ParseDeclaratorInternal(clang::Declarator&, void
(clang::Parser::*)(clang::Declarator&)) (/lib64/libclang-cpp.so.12+0xa242e1)
clang-12: error: unable to execute command: Segmentation fault (core dumped)
clang-12: error: clang frontend command failed due to signal (use -v to see
invocation)

I can also confirm over on Godbolt that this seems to crash trunk Clang too:
https://godbolt.org/z/j84dKe5qT

Final note, `clang -c test.c` makes the error completely silent (e.g. the
output makes it seem as though compiling was successful, although the return
value is at least 255), which seems especially odd.

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