jfb marked an inline comment as done.
jfb added inline comments.
================
Comment at: clang/test/CodeGen/union-tail-padding.c:28-36
+union Front {
+ int i;
+ long long ll;
+};
+
+union Front front1;
+union Front front2 = {}; // expected-warning {{Initializing union
'Front' field 'i' only initializes the first 4 of 8 bytes, leaving the
remaining 4 bytes undefined}}
----------------
dexonsmith wrote:
> Are these warnings actionable? What should users do when they see this
> warning?
Good point!
I was thinking about this, and was wondering if I should add a fixit which
suggests using the first wider member of the union. The problem is to offer the
same object representation... that's tricky on its own (there isn't always an
exact match), and then we have to deal with type punning (in C++, not in C).
So I'd love ideas, because I'm not sure what to do. That being said, I wrote
this partly because D68115 was surprising to folks, and partly because
developers would like to opt-in to this diagnostic to find places where
initialization isn't doing what they think.
Maybe instead we should suggest to leave uninitialized, and use an assignment,
or `memset`?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D80055/new/
https://reviews.llvm.org/D80055
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