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https://issues.apache.org/jira/browse/THRIFT-6337?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sylwester Lachiewicz updated THRIFT-6337:
-----------------------------------------
Priority: Minor (was: Major)
> A typedef cycle makes the compiler loop forever instead of reporting an error
> -----------------------------------------------------------------------------
>
> Key: THRIFT-6337
> URL: https://issues.apache.org/jira/browse/THRIFT-6337
> Project: Thrift
> Issue Type: Bug
> Components: Compiler (General)
> Affects Versions: 0.25.0
> Reporter: Sylwester Lachiewicz
> Priority: Minor
>
> Two typedefs that name each other, both declared before their target is
> known, are accepted by the parser and hang the compiler in
> [t_type::get_true_type|https://github.com/apache/thrift/blob/master/compiler/cpp/src/thrift/parse/parse.cc#L29],
> which follows typedefs until it reaches a non-typedef and never does.
> {code}
> typedef B A
> typedef A B
> {code}
> {noformat}
> $ thrift --gen json repro.thrift
> (runs until killed)
> {noformat}
> On the two-line file only {{--gen json}} hangs; {{cpp}}, {{java}}, {{py}},
> {{html}} and {{netstd}} exit 0 because they never resolve an unused typedef.
> Once a struct field uses either name ({{struct S { 1: A a }}}), every
> generator tried hangs except {{html}}. {{typedef T T}} and {{typedef list<L>
> L}} behave the same. The parser only catches the case where the first name is
> already defined ({{Type "A" is already defined.}}); a forward reference goes
> through
> [t_typedef::get_type|https://github.com/apache/thrift/blob/master/compiler/cpp/src/thrift/parse/t_typedef.cc#L28],
> which resolves lazily and has no cycle check. The Go front end on the same
> input reports the cycle.
> Reproduced on master at 1ae43c8ae. Fixed by [PR
> #3925|https://github.com/apache/thrift/pull/3925] for
> [THRIFT-6333|https://issues.apache.org/jira/browse/THRIFT-6333], which
> resolves every type at the end of parsing and reports {{Type "A" refers to
> itself}}.
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