[llvm-bugs] [Bug 45734] New: missing warning for uninitialized struct member

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45734

            Bug ID: 45734
           Summary: missing warning for uninitialized struct member
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: arnd at linaro.org
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

Test-building linux kernels, I found new bugs with gcc-10 that neither older
gcc versions nor clang report. See this example at https://godbolt.org/z/pYDWPx

struct s {
    int a; // always initialized
    int b; // partially initialized, gcc-10 warns
    int c; // not initialized, no warning
};

void f(void *p, int flag)
{
    struct s s;

    s.a = 0;
    if (flag)
        s.b |= 1;
    else
        s.b &= ~1;

    __builtin_memcpy(p, &s, sizeof(s));
}

Ideally there would be a warning for both s.b and s.c, but clang currently
warns for neither struct member.

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