jextract fails to parse stdatomic.h

[Artem Ananev]

Hi Maurizio, 

thank you for quick response.

Is there a workaround to this issue? Will it be addressed in the final version of FFI / jextract?

From what I saw during debugging, your assumption about the underlying problem looks right. In TypeImpl class there is a field `layoutMaker`, which implements a type visitor. When this issue with atomic_flag happens, this visitor throws an unsupported exception from its visitType() method.

Thanks,
Artem

> On Oct 19, 2023, at 5:05 PM, Maurizio Cimadamore <maurizio.cimadamore at oracle.com> wrote:
> 
> Hi Artem,
> thanks for the report. This issue is probably a latent one, which has been made manifest by a recent PR:
> 
> https://git.openjdk.org/jextract/pull/121
> 
> I believe the underlying cause is that there is some type involved in this declaration is not supported (meaning we can't generate a layout for it). This causes the layout to be dropped from the struct. But now we have a size mismatch, as clang is reporting that the size of the struct is 1 byte, but, since we end up with an empty struct layout, our size is zero.
> 
> If I had to guess (given the headers involved), I'd say that the Atomic type kind is not supported by TypeMaker.
> 
> Probably related to this old issue:
> https://mail.openjdk.org/pipermail/panama-dev/2019-May/005387.html
> 
> Maurizio
> 
> On 20/10/2023 00:42, Artem Ananev wrote:
>> Hi,
>> 
>> I use jextract version "JDK version 21+35-LTS-2513” on a Ubuntu 22.04.3 box. It fails with the following error:
>> 
>> ```
>> java.lang.AssertionError: Unexpected size for layout []. Found 0 ; expected 1
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.RecordLayoutComputer.checkSize(RecordLayoutComputer.java:198)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.StructLayoutComputer.finishRecord(StructLayoutComputer.java:142)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.RecordLayoutComputer.compute(RecordLayoutComputer.java:114)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.RecordLayoutComputer.computeInternal(RecordLayoutComputer.java:89)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.RecordLayoutComputer.compute(RecordLayoutComputer.java:71)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.TreeMaker.createRecord(TreeMaker.java:205)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.TreeMaker.createTreeInternal(TreeMaker.java:104)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.TreeMaker.createTree(TreeMaker.java:93)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.Parser.lambda$parse$2(Parser.java:86)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.clang.Cursor$CursorChildren$Context.visit(Cursor.java:223)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.clang.Cursor$CursorChildren.lambda$static$0(Cursor.java:242)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.clang.libclang.Index_h.clang_visitChildren(Index_h.java:5108)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.clang.Cursor$CursorChildren.forEach(Cursor.java:254)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.clang.Cursor.forEach(Cursor.java:194)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.impl.Parser.parse(Parser.java:64)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.JextractTool.parse(JextractTool.java:116)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.JextractTool.run(JextractTool.java:466)
>> 	at org.openjdk.jextract at 21/org.openjdk.jextract.JextractTool.main(JextractTool.java:174)
>> Unrecoverable uncaught exception encountered. The VM will now exit
>> ```
>> 
>> There is no way to understand where exactly it fails, so I downloaded jextract sources, ran it in debug mode, and found the error happens when it’s parsing <stdatomic.h>, in particular this line:
>> 
>> ```
>> typedef struct atomic_flag { atomic_bool _Value; } atomic_flag;
>> ```
>> 
>> If I comment out this line (and all other declarations in the same header that depend on atomic_flag), jextract no longer fails. Note that this header is a part of jextract distribution, it’s in <jextract home>/conf/jextract/stdatomic.h
>> 
>> Steps to reproduce:
>> 
>> ```
>> echo '#include <stdatomic.h>' >/tmp/test.h && jextract --source /tmp/test.h
>> ```
>> 
>> Thanks,
>> Artem
>>