I'm trying to call fs.change_rev_prop2 (https://goo.gl/6b6TG5) from Python / SWIG - and apparently can't figure out how to pass old_value_p as what I'm assuming needs to be a double pointer from Python.
(Also posted to http://stackoverflow.com/q/32239234/751158 . Looking for more visibility, and/or for someone here to earn a bounty there that I've already posted.) Minimized code sample: #!/usr/bin/env python from svn import repos, fs, core fs_ptr = repos.fs(repos.open("/opt/app/svn/repos/test")) rev_num = 1 user = fs.revision_prop(fs_ptr, rev_num, "svn:author") # Works, but is is deprecated in favor of fs.change_rev_prop2 . fs.change_rev_prop(fs_ptr, rev_num, "svn:author", user.lower()) # fs.change_rev_prop2(fs_ptr, rev_num, "svn:author", user, user.lower()) # > svn.core.SubversionException: 160049 - revprop 'svn:author' has unexpected value in filesystem # fs.change_rev_prop2(fs_ptr, rev_num, "svn:author", None, user.lower()) # Per svn_ra.h: If the capability is not advertised, then @a old_value_p MUST be @c NULL. # This results in a successful change of the revision property, but then this program ends with a segmentation fault. Details of the # 160049 error: Traceback (most recent call last): File "./normalize-usernames.py", line 10, in <module> fs.change_rev_prop2(fs_ptr, rev_num, "svn:author", user, user.lower()) File "/opt/app/subversion/lib/svn-python/libsvn/fs.py", line 711, in svn_fs_change_rev_prop2 return _fs.svn_fs_change_rev_prop2(*args) svn.core.SubversionException: 160049 - revprop 'svn:author' has unexpected value in filesystem I believe the value I'm attempting to pass is "correct". After all, I'm obtaining it from the API immediately before attempting to set it back. I'm assuming I'm just not passing the value correctly in a way that the native API can accept it. So I could just continue using change_rev_prop - but it is clearly marked as deprecated in the API ("Provided for backward compatibility with the 1.6 API"). Should be able to do better, though... Interestingly, calling change_rev_prop2 with None for old_value_p results in the desired change taking effect in the repository - but not without causing the Python program to then immediately terminate with a Segmentation Fault. It would seem that I need to pass the old / current value as a pointer - possibly to be able to differentiate to the API the difference between a null pointer (value not provided) and a pointer to a null value (value is provided, but value is null)? However, I've tried all the combinations I can think of here without success - including using various wrappers from ctypes. StackOverflow is appropriately suggesting a good number of questions that may already have the answer here - but it appears that most of them cover cases where the author has control over the C sources and with recommendations to alter the C API to avoid the complexity entirely - which I don't see to be an option here. This is largely my only experience with Python and SWIG so far, and any tips would be appreciated, thanks!
