[foreign-jextract] RFR: 8249536: jextract throw IllegalStateException for bitfields in nested anonymous structs
Jorn Vernee
jvernee at openjdk.java.net
Wed Jul 15 20:33:09 UTC 2020
On Wed, 15 Jul 2020 19:48:39 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:
>> Hi,
>>
>> This patch fixes an issue with grouping of bitfields into a container for structs that contain anonymous nested structs
>> that have bitfields in them. Such as
>> struct Foo {
>> struct {
>> int a : 7;
>> int b : 25;
>> };
>> };
>>
>> The current code iterates over the member layouts of a struct, and when it finds a bitfield storage unit, it tries to
>> find matching bitfield Declarations and groups them into a synthetic nested BITFIELDS declaration.
>> But, the memory layout members also contain bitfields that are found in anonymous nested structs, since they are
>> flattened into the parent layout. However, for the jextract Declaration tree this is not the case, so the current code
>> can not find a matching declaration for these bitfield layouts. e.g. in the example `Foo` will have a bitfield storage
>> unit which contains `a` and `b`, but the Declaration tree has the declarations for `a` and `b` nested inside the
>> anonymous struct (layouts and declaration tree are different in this regard). The fix is to ignore bitfields that come
>> from nested anonymous structs. They will be handled when processing the nested anonymous struct instead. Thanks, Jorn
>
> What happens for the following?
> struct Foo {
> struct {
> int a : 7;
> int b : 25;
> };
> struct Bar {
> int a : 12;
> } bar;
> };
>
>
> What happens for the following?
>
> ```c
> struct Foo {
> struct {
> int a : 7;
> int b : 25;
> };
> struct Bar {
> int a : 12;
> } bar;
> };
> ```
In that case there is no problem since the `bar` struct is not anonymous.
You get the following tree (On Windows):
Scoped: TOPLEVEL <toplevel>
Scoped: STRUCT Foo layout =
[b32[contents=[b7(a)[layout/name=a]b25(b)[layout/name=b]],abi/windows/class=INTEGER][b32[contents=[b12(a)[layout/name=a]x20],abi/windows/class=INTEGER]](bar)[layout/name=bar]](Foo)[layout/name=Foo]
Scoped: STRUCT layout = [b32[contents=[b7(a)[layout/name=a]b25(b)[layout/name=b]],abi/windows/class=INTEGER]]
Scoped: BITFIELDS layout = [b7(a)[layout/name=a]b25(b)[layout/name=b]]
Variable: BITFIELD a type = Int(layout = b32[abi/windows/class=INTEGER]), layout = Optional[b7]
Variable: BITFIELD b type = Int(layout = b32[abi/windows/class=INTEGER]), layout = Optional[b25]
Scoped: STRUCT Bar layout = [b32[contents=[b12(a)[layout/name=a]x20],abi/windows/class=INTEGER]](Bar)[layout/name=Bar]
Scoped: BITFIELDS layout = [b12(a)[layout/name=a]x20]
Variable: BITFIELD a type = Int(layout = b32[abi/windows/class=INTEGER]), layout = Optional[b12]
Variable: FIELD bar type =
Declared([b32[contents=[b12(a)[layout/name=a]x20],abi/windows/class=INTEGER]](Bar)[layout/name=Bar]), layout =
Optional[[b32[contents=[b12(a)[layout/name=a]x20],abi/windows/class=INTEGER]](Bar)[layout/name=Bar]]
-------------
PR: https://git.openjdk.java.net/panama-foreign/pull/246
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