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https://issues.apache.org/jira/browse/THRIFT-4846?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16811196#comment-16811196
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Todd Lipcon commented on THRIFT-4846:
-------------------------------------
Attached patch implements the sort and the failure for when the DAG is
unsortable:
{code}
todd@todd-ThinkPad-P51:/src/thrift$ cat cycle.thrift
struct A {
1:B a_field;
}
struct B {
1:A b_field;
}
todd@todd-ThinkPad-P51:/src/thrift$ ./compiler/cpp/thrift -gen cpp
cycle.thrift
[WARNING:generation:1] Found cycle in structs: A.a_field -> B.b_field -> A
[WARNING:generation:1] Thrift file contains struct cycles, which may not be
supported in all languages. Consider using reference fields. For example:
1: Foo& my_field;
[FAILURE:generation:1] Cyclic references not supported by target language
{code}
> C++ generator should topologically sort struct definitions and error on cycles
> ------------------------------------------------------------------------------
>
> Key: THRIFT-4846
> URL: https://issues.apache.org/jira/browse/THRIFT-4846
> Project: Thrift
> Issue Type: Bug
> Reporter: Todd Lipcon
> Priority: Major
> Attachments: thrift-4846.patch
>
>
> C++ (and maybe other languages?) treat Thrift struct-typed fields as plain
> struct members of the containing struct. Currently, the generator outputs the
> types in the same order as they're defined in the underlying Thrift field,
> which means that a file like:
> {code}
> struct A {
> 1: B foo;
> }
> struct B {
> }
> {code}
> will generate C++ code that fails to compile.
> We should topologically-sort the structs before outputting the definitions so
> that the generated code compiles correctly.
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