Union Initializer Fails During CIRGen

[bruteforceboy]

The following code snippet fails when generating CIR, and that didn't happen until PR#1007 was merged.

typedef struct {
  union {
    int a;
    long b;
  };
} S;

S s = { .a = 1 };

It seems there is some extra padding even after unpacking the union, and there is an error when computing the size?

I tried to fix it myself, but then it fails again when lowering to LLVM, because b is marked as inactive, and a is the "active" field, but when lowering to LLVM, the type converter uses the larger member of the union.

cc: @bcardosolopes and @ChuanqiXu9 since you authored the PR)

[ChuanqiXu9]

Maybe we shouldn't go into

clangir/clang/lib/CIR/CodeGen/CIRGenExprConst.cpp

Lines 410 to 416 in 3aed38c

	} else if (DesiredSize > AlignedSize) {
	// The natural layout would be too small. Add padding to fix it. (This
	// is ignored if we choose a packed layout.)
	UnpackedElemStorage.assign(UnpackedElems.begin(), UnpackedElems.end());
	UnpackedElemStorage.push_back(Utils.getPadding(DesiredSize - Size));
	UnpackedElems = UnpackedElemStorage;
	}

when we're making union in the above branch?

I'd like to look into the details a few days later.

[bcardosolopes]

cc @gitoleg

[ChuanqiXu9]

Sent #1160