[cfe-dev] Missing -Wshorten-64-to-32 for operator+=

[Shoaib Meenai via cfe-dev]

I'd filed https://bugs.llvm.org/show_bug.cgi?id=33559 for this quite a while back, although I never got the chance to look into it more.

On 7/27/20, 9:04 PM, "cfe-dev on behalf of John McCall via cfe-dev" <cfe-dev-bounces at lists.llvm.org on behalf of cfe-dev at lists.llvm.org> wrote:

    On 24 Jul 2020, at 5:04, Milan Kříž via cfe-dev wrote:
    > Hi,
    >
    > I have found that operator+= doesn't fire -Wshorten-64-to-32 warning, 
    > while pure opreator+ fires it. See the following example:
    >
    > #include <stdint.h>
    >
    > int main()
    > {
    >     uint32_t test = 0;
    >     uint64_t test64 = UINT32_MAX + 1;
    >     test += test64;// doesn't fire the warning
    >     test = test + test64; // fires the warning: implicit conversion 
    > loses integer precision: 'unsigned long' to 'uint32_t' (aka 'unsigned 
    > int') [-Wshorten-64-to-32]
    > }
    >
    > I've found this in 32-bit build while adding uint64_t to size_t 
    > (size_t has 4 byte on 32-bit) variable (Clang didn't warn me while 
    > MSVC surprisingly did :-)).
    >
    > Should I post a bug-report or is it some known exception where the 
    > warning should not occur?

    Please file a bug.  There’s no reason for the warning to not fire on 
    compound operators like it would on the expanded form.

    John.

    >
    > Mi-L@
    >
    >
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