anonymous unions and designated initializers do not work together

[llvmbot]

Bugzilla Link	3778
Resolution	FIXED
Resolved on	Mar 12, 2010 00:57
Version	unspecified
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@tkremenek

Extended Description

In one of the data structures of coreboot we use an anonymous union with additional information depending on the .type field of that structure. It seems the static analyzer does not like that:

static.c:57:44: error: field designator 'apic_cluster' refers to a member of an anonymous union
.path = {.type=DEVICE_PATH_APIC_CLUSTER,{.apic_cluster={ .cluster = 0x0 }}},
^
In file included from static.c:1:
In file included from /home/patrick/work/coreboot-v2/src/include/device/device.h:6:
/home/patrick/work/coreboot-v2/src/include/device/path.h:69:28: note: field designator refers here
struct apic_cluster_path apic_cluster;
^

What's funny about this is that it does know which field in the anonymous union the code refers to, but it considers it wrong.

Please let me know what information you need and I will try to get it to you.

This is an open source firmware, and we have a test run of all our targets here:
http://coreboot.org/~stepan/llvm/coreboot-builds

We plan to use the static analyzer in a checkin hook as soon as we managed to get rid of the parser rejects.

[llvmbot]

assigned to @DougGregor

[DougGregor]

This code is ill-formed according to C99, since anonymous unions are a GNU extension to C. However, we try to be compatible with GNU, so if you can attach a reduced test case, we can make sure this works and downgrade the error to an extension warning.

[llvmbot]

Oh, I didn't know this is GNU only. Been around with the GNU folks for too long. Yet, it's a very useful thing.

Here's a test case that reproduces the problem:
struct pci_path {
unsigned devfn;
};
struct device_path {
union { struct pci_path pci; };
};
struct device_path my_device = {
{ .pci = { .devfn = 10 } }
};

[llvmbot]

test case
ok, the second struct is of course not needed, so here's a further reduced version

[DougGregor]

Fixed here:

http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20090413/015590.html