[LLVMbugs] [Bug 14247] New: -fcatch-undefined-behavior should allow severity levels and recoverability

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=14247

             Bug #: 14247
           Summary: -fcatch-undefined-behavior should allow severity
                    levels and recoverability
           Product: clang
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: htam at apple.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Clang should support one or both of the following:
1.  An option to turn -fcatch-undefined-behavior traps into run-time warnings
or at least recoverable traps
(-fbreak-undefined-behavior/-fwarn-undefined-behavior?).  The former would
allow a programmer to quickly get a sense of issues in the entire program by
just by piping through uniq.  The second would allow someone to get through a
few warnings at a time in a debugger.
2.  Fine-grained control on which types of UB are caught; similar to
-Werror=/-Wno-error= (-f[no-]catch-udefined-behavior=X?).

Motivation:
I'm using clang built with compiler-rt on x86_64 Linux.  All are from trunk at
r167261.  The -fcatch-undefined-behavior option emits an irrecoverable trap,
even when debugging a program under gdb.  In the program I am trying to debug
with -fcatch-undefined-behavior, there are a large number of "1 << 31"
operations that cause the program to terminate very early in the run.  This is
preventing me from investigating more important UB later on in the program.

I know that this is, strictly speaking, undefined behavior, but it is
exceedingly unlikely to be the cause of the bug I'm looking for.  Instead of
fixing one issue at a time, being able to get a list of all the undefined
behavior points would make it much easier to triage bugs in large, legacy
programs.

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