[Python-Dev] Move encoding_decl to the top of Grammar/Grammar? (original) (raw)
Thomas Lee tom at vector-seven.com
Tue Dec 2 07:57:11 CET 2008
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Hi all,
Currently, Parser/parsetok.c has a dependency on graminit.h. This can cause headaches when rebuilding after adding new syntax to Grammar/Grammar because parsetok.c is part of pgen, which is responsible for generating graminit.h.
This circular dependency can result in parsetok.c using a different value for encoding_decl to what is used in ast.c, which causes PyAST_FromNode to fall over at runtime. It effectively looks something like this:
- Grammar/Grammar is modified
- build begins -- pgen compiles, parsetok.c uses encoding_decl=X
- graminit.h is rebuilt with encoding_decl=Y
- ast.c is compiled using encoding_decl=Y
- when python runs, parsetok() emits encoding_decl nodes that PyAST_FromNode can't recognize:
SystemError: invalid node XXX for PyAST_FromNode
A nice, easy short term solution that doesn't require unwinding this dependency would be to simply move encoding_decl to the top of Grammar/Grammar and add a big warning noting that it needs to come before everything else. This will help to ensure its value never changes when syntax is added/removed.
I'm happy to provide a patch for this (including some additional dependency info for files dependent upon graminit.h and Python-ast.h), but was wondering if there were any opinions about how this should be resolved.
Cheers, Tom
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