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| 14:23.27 | blast007 | would someone help me figure out why this is crashing/erroring? https://gist.github.com/blast007/2a9b41d18121f391fc34ffdc61f8aec1 Trying to replace our custom PNG reader with libpng, and that passes a std::isteam/std::ifstream to the PNGImageFile constructor. So the problem is something with my custom read function that is supposed to make libpng read from that std::istream instead of a file itself. |
| 14:29.09 | blast007 | terminate called after throwing an instance of 'std::ios_base::failure[abi:cxx11]' |
| 14:29.12 | blast007 | <PROTECTED> |
| 14:29.55 | blast007 | that gets triggered when it calls png_read_info, which is the first thing to use the customRead function |
| 14:37.21 | blast007 | output of valgrind: http://paste.debian.net/hidden/7ee2240b/ |
| 15:56.42 | macsforme | did you try checking std::ifstream::is_open() in addition to checking for a valid pointer and object? |
| 16:05.25 | macsforme | and do you know for sure that std::istream::read() is virtual? you're casting a std::ifstream to a std::istream before calling read() |
| 16:11.52 | blast007 | added an is_open() check in main() and it still bombs |
| 16:13.35 | blast007 | it does read the signature at line 50 correctly - does that answer your second question? |
| 16:18.05 | blast007 | I was basing it off of this: http://www.piko3d.net/tutorials/libpng-tutorial-loading-png-files-from-streams/ |
| 16:19.19 | blast007 | (do note that some of their code formatting is messed and has raw HTML entities showing instead of the intended symbols, like & for & and < for <) |
| 18:44.22 | JeffM | if you just make a sample project with the tutorial code, does it work? |
| 19:07.25 | blast007 | that gist is pretty close to what that is |
| 19:08.43 | blast007 | I'll try copying their code verbatim though |
| 19:18.26 | blast007 | segfaults trying to do the read inside userReadData |
| 19:30.32 | blast007 | valgrind again reports an "Invalid read of size 8" |
| 19:30.58 | blast007 | (when trying to ->read from the stream inside the userReadData function) |
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| 22:51.52 | blast007 | okay.. I extended std::ifstream with my own input class, adding a public std::string class variable. It gets set as part of the call to the constructor in main(), and is still accessible within the PNGImageFile constructor. But the object that gets pulled in via png_get_io_ptr() in the customRead method has a blank value set for that std::string. |
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