[llvm-bugs] [Bug 52270] New: UBSan is inconsistent about erroring on dead code in ternary operator branches

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52270

            Bug ID: 52270
           Summary: UBSan is inconsistent about erroring on dead code in
                    ternary operator branches
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: regehr at cs.utah.edu
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

https://gcc.godbolt.org/z/WxKjWMo47

in this example program (supplied by Pascal Cuoq), UBSan should either error in
both cases, or in neither of them (I would argue that it should not error in
either case, but ymmv):

void f(int a) {
  a ? 0 : 0x7fffffff + 1;
}

void g(int a) {
  a ? 0 : 0 >> 32;
}

int main(void) {
    f(1);
    g(1);
}

instead, however, UBSan errors on the shift bug, but not on the overflowing
addition. when this program is run, this is the output we see:

/app/example.c:6:13: runtime error: shift exponent 32 is too large for 32-bit
type 'int'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /app/example.c:6:13 in

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