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clang assertion failure when trying to infer generic lambda return type from undefined variable #25179

Open Quuxplusone opened 9 years ago

Quuxplusone commented 9 years ago
Bugzilla Link PR25180
Status NEW
Importance P normal
Reported by Fabian Gruber (fabian.gruber@fadeopolis.com)
Reported on 2015-10-14 08:58:17 -0700
Last modified on 2015-10-14 08:58:17 -0700
Version trunk
Hardware PC Linux
CC llvm-bugs@lists.llvm.org
Fixed by commit(s)
Attachments clang_bug-6b2789.cpp (786 bytes, text/x-c++src)
Blocks
Blocked by
See also

Created attachment 15080 Test case cpp file that triggers the assertion failure

Clang dies with an assertion failure in the frontend while trying to infer the type of a generic lambda. The lambda consists of an if-statement in which the else branch is just `return baz;' where baz is an undefined variable.

This only happens when compiling with -std=c++14'. With-std=c++11' an undefined variable error is reported.

I managed to reproduce this bug with the Ubuntu clang/llvm 3.8 package from llvm.org [3.8.0-svn250077-1~exp1 (trunk)] and a version built from trunk [(http://llvm.org/git/clang.git 52bc812d7e056333f2a456b8fe8a0dba93e09bfd)(http://llvm.org/git/llvm.git 0dcd516b64fa28ad83e5df4c71c5852cfe9d5683)].

== preprocessed testcase:

1 ""

1 "clang_bug.cpp"

bool quoz();

int foo() { auto bar = []() { if (quoz()) { // The bug is also triggered even if there are compiler errors in this // branch of the if-statement. // I.e. using an undefined variable, etc. // The error mustn't be `severe' enough to stop clang from looking at the // else-branch, though.

  // in trunk clang-3.8 (52bc812d7e056333f2a456b8fe8a0dba93e09bfd) the bug
  // is not triggered if the if-statement is not present.
  // on clang-3.8 from the LLVM Ubuntu repo (3.8.0-svn250077-1~exp1) just
  // `return baz` is enough.

  return "default";
} else {
  // `baz' is not defined in this scope!
  // If I define name it stops crashing.
  return baz;
}

}; }

== crash reproducer for trunk clang = (http://llvm.org/git/clang.git 52bc812d7e056333f2a456b8fe8a0dba93e09bfd) = (http://llvm.org/git/llvm.git 0dcd516b64fa28ad83e5df4c71c5852cfe9d5683)

Crash reproducer for clang version 3.8.0 (http://llvm.org/git/clang.git 52bc812d7e056333f2a456b8fe8a0dba93e09bfd) (http://llvm.org/git/llvm.git 0dcd516b64fa28ad83e5df4c71c5852cfe9d5683)

Driver args: "-std=c++14" "clang_bug.cpp"

Original command: "/home/fader/workspace/.build/debug/llvm/bin/clang-3.8" "-cc1" "-triple" "x86_64-unknown-linux-gnu" "-emit-obj" "-mrelax-all" "-disable-free" "-main-file-name" "clang_bug.cpp" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-fmath-errno" "-masm-verbose" "-mconstructor-aliases" "-munwind-tables" "-fuse-init-array" "-target-cpu" "x86-64" "-dwarf-column-info" "-resource-dir" "/home/fader/workspace/.build/debug/llvm/bin/../lib/clang/3.8.0" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/x86_64-linux-gnu/c++/4.9" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/x86_64-linux-gnu/c++/4.9" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/backward" "-internal-isystem" "/usr/local/include" "-internal-isystem" "/home/fader/workspace/.build/debug/llvm/bin/../lib/clang/3.8.0/include" "-internal-externc-isystem" "/usr/include/x86_64-linux-gnu" "-internal-externc-isystem" "/include" "-internal-externc-isystem" "/usr/include" "-std=c++14" "-fdeprecated-macro" "-fdebug-compilation-dir" "/home/fader/Desktop" "-ferror-limit" "19" "-fmessage-length" "134" "-fobjc-runtime=gcc" "-fcxx-exceptions" "-fexceptions" "-fdiagnostics-show-option" "-fcolor-diagnostics" "-o" "/tmp/clang_bug-64f932.o" "-x" "c++" "clang_bug.cpp"

"/home/fader/workspace/.build/debug/llvm/bin/clang-3.8" "-cc1" "-triple" "x86_64-unknown-linux-gnu" "-emit-obj" "-mrelax-all" "-disable-free" "-main-file-name" "clang_bug.cpp" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-fmath-errno" "-masm-verbose" "-mconstructor-aliases" "-munwind-tables" "-fuse-init-array" "-target-cpu" "x86-64" "-dwarf-column-info" "-std=c++14" "-fdeprecated-macro" "-ferror-limit" "19" "-fmessage-length" "134" "-fobjc-runtime=gcc" "-fcxx-exceptions" "-fexceptions" "-fdiagnostics-show-option" "-fcolor-diagnostics" "-x" "c++" "clang_bug-6b2789.cpp"

== crash reproducer for clang from llvm.org Ubuntu package

Crash reproducer for Ubuntu clang version 3.8.0-svn250077-1~exp1 (trunk) (based on LLVM 3.8.0)

Driver args: "-std=c++14" "clang_bug.cpp"

Original command: "/usr/lib/llvm-3.8/bin/clang" "-cc1" "-triple" "x86_64-pc-linux-gnu" "-emit-obj" "-mrelax-all" "-disable-free" "-disable-llvm-verifier" "-main-file-name" "clang_bug.cpp" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-fmath-errno" "-masm-verbose" "-mconstructor-aliases" "-munwind-tables" "-fuse-init-array" "-target-cpu" "x86-64" "-target-linker-version" "2.25" "-dwarf-column-info" "-resource-dir" "/usr/lib/llvm-3.8/bin/../lib/clang/3.8.0" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/x86_64-linux-gnu/c++/4.9" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/x86_64-linux-gnu/c++/4.9" "-internal-isystem" "/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/backward" "-internal-isystem" "/usr/local/include" "-internal-isystem" "/usr/lib/llvm-3.8/bin/../lib/clang/3.8.0/include" "-internal-externc-isystem" "/usr/include/x86_64-linux-gnu" "-internal-externc-isystem" "/include" "-internal-externc-isystem" "/usr/include" "-std=c++14" "-fdeprecated-macro" "-fdebug-compilation-dir" "/home/fader/Desktop" "-ferror-limit" "19" "-fmessage-length" "134" "-fobjc-runtime=gcc" "-fcxx-exceptions" "-fexceptions" "-fdiagnostics-show-option" "-fcolor-diagnostics" "-o" "/tmp/clang_bug-9f98d4.o" "-x" "c++" "clang_bug.cpp"

"/usr/lib/llvm-3.8/bin/clang" "-cc1" "-triple" "x86_64-pc-linux-gnu" "-emit-obj" "-mrelax-all" "-disable-free" "-disable-llvm-verifier" "-main-file-name" "clang_bug.cpp" "-mrelocation-model" "static" "-mthread-model" "posix" "-mdisable-fp-elim" "-fmath-errno" "-masm-verbose" "-mconstructor-aliases" "-munwind-tables" "-fuse-init-array" "-target-cpu" "x86-64" "-target-linker-version" "2.25" "-dwarf-column-info" "-std=c++14" "-fdeprecated-macro" "-ferror-limit" "19" "-fmessage-length" "134" "-fobjc-runtime=gcc" "-fcxx-exceptions" "-fexceptions" "-fdiagnostics-show-option" "-fcolor-diagnostics" "-x" "c++" "clang_bug-a32268.cpp"

Quuxplusone commented 9 years ago

Attached clang_bug-6b2789.cpp (786 bytes, text/x-c++src): Test case cpp file that triggers the assertion failure