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2016-02-17Separate static allocator from payload function interpositionsAdrian Kummerlaender
2016-02-17Implement static allocator for initializationAdrian Kummerlaender
The previous interposition logic based on plain usage of `dlsym` analogously to various online examples led to a deadlock during _neovim_ startup. This deadlock was caused by _neovim_'s custom memory allocation library _jemalloc_ because it calls `mmap` during its initialization phase. The problem with calling `mmap` during initialization is that this already leads to executing `libChangeLog`'s `mmap` version whoes static `actual_mmap` function pointer is not initialized at this point in time. This is detected and leads to a call to `dlsym` to remedy this situation. Sadly `dlsym` in turn requires memory allocation using `calloc` which leads us back to initializing _jemalloc_ and as such to a deadlock. I first saw this as a bug in _jemalloc_ which seemed to be confirmed by a short search in my search engine of choice. This prompted me to create an appropriate [bug report](https://github.com/jemalloc/jemalloc/issues/329) which was dismissed as a problem in the way `mmap` was interposed and not as a bug in the library. Thus it seems to be accepted practice that it is not the responsibility of a custom memory allocator to cater to the initialization needs of other libraries relying on function interposition. This is of course a valid position as the whole issue is a kind of _chicken and egg_ problem where both sides can be argued. To cut to the chase I was left with the only option of working around this deadlock by adapting `libChangeLog` to call `dlsym` without relying on the wrapped application's memory allocator of choice. The most straight forward way to do this is to provide another custom memory allocator alongside the _payload_ function interpositions of `mmap` and friends. `init/alloc.cc` implements such a selectively transparent memory allocator that offers a small static buffer for usage in the context of executing `dlsym`.The choice between forwarding memory allocation requests to the wrapped application's allocator and using the static buffer is governed by `init::dlsymContext`. This tiny helper class maintains an `dlsym_level` counter by posing as a scope guard. The end result of this extension to `libChangeLog` is that it now also works with applications using _jemalloc_ such as _neovim_ and should overall be much more robust during its initialization phase.
2016-02-16Move actual function pointers to function local static variablesAdrian Kummerlaender
The previous approach of storing them in static variables of the `actual` namespace and initializing them statically did not work out as it is not guaranteed that they are initialized before any interposed function is called.
2016-02-16Adapt `get_actual_function` template to accept newly introduced `function_ptr`Adrian Kummerlaender
2016-02-16Replace `std::function` with raw function pointerAdrian Kummerlaender
2016-02-15Add support for commenting ignore patterns fileAdrian Kummerlaender
All lines starting with `#` are interpreted as comments
2016-02-14Implement support for excluding arbitrary paths from trackingAdrian Kummerlaender
The library may be provided with a new-line separated list of regular expressions via the newly introduced `CHANGE_LOG_IGNORE_PATTERN_PATH`. Any proposed tracking path that is matched by any of the provided patterns is excluded from change reporting. This functionality uses the Standard's regular expression parsing functionality and as such doesn't introduce any new dependencies. If no file path is provided or the provided file path is unreadable all paths will be tracked. `change` was adapted to set `CHANGE_LOG_IGNORE_PATTERN_PATH` to `.change_log_ignore` which means that it will by default exclude any patterns provided via this file in the current working directory. An example for such a file customized for hiding _vim_'s internal write logic may look as follows: [0-9]+ [^~]*~ [.*\.viminfo .*\.swp Note that this is implemented in a fashion where it is not guaranteed that the full _canonical_ path is checked against the patterns. It remains to be decided if this is enough for all common use cases of this new functionality. `tracking::PathMatcher` lacks any explicit thread synchronization - according to my current knowledge this should not be necessary as we are only ever reading the private `std::vector<std::regex>` instance. If invalid regular expressions are provided they are silently ignored.
2016-02-14Reduce `ChangeTracker` public _interface_ to `track`Adrian Kummerlaender
2016-02-13Add filesystem exception handling where requiredAdrian Kummerlaender
2016-02-13Reimplement locking in `Logger::append`Adrian Kummerlaender
2016-02-11Delay tracking activationAdrian Kummerlaender
Introduce global static `enabled` variable used to signal the interposed functions to either start tracking or perform plain forwarding without any additional logic. This is required as e.g. `nvim` crashed when wrapped in `libChangeLog` because it called interposed functions during library initialization.
2016-02-11Extract file descriptor filter logicAdrian Kummerlaender
2016-02-11Extract child emplacement into thread safe memberAdrian Kummerlaender
2016-02-10Replace macro argument expansion with more idiomatic recursive templateAdrian Kummerlaender
2016-02-07Increase log message generation readabilityAdrian Kummerlaender
2016-02-06Prevent deleted files from being displayed using `diff`Adrian Kummerlaender
2016-02-06Track `writev` system callAdrian Kummerlaender
2016-02-06Preserve pre-change file content as tracking stateAdrian Kummerlaender
Relying on `diff` for storing the pre-change content did not work out as it opens the file descriptors to soon and only reads the first block of pre-change file content until the remaining content is actually required. This obviously led to problems when tracking actually changing files.
2015-12-27Introduce thread synchronization for tracking init and loggingAdrian Kummerlaender
This obviously leads to synchronizing syscalls that would otherwise happen in parallel. Luckily the goal of this library is to monitor file changes performed by single, user facing applications and as such it doesn't matter if some operations are slightly slower.
2015-12-27Explicitly set log file permissionsAdrian Kummerlaender
This ensures that the log file is actually accessable - there was a problem where e.g. `change rm test` did not create the log file correctly.
2015-12-24Prevent the libraries own log writes from being trackedAdrian Kummerlaender
2015-12-24Add path label for the file provided via standard inputAdrian Kummerlaender
2015-12-24Use full path for change trackingAdrian Kummerlaender
Prevents the same file being tracked multiple times due to relative input paths.
2015-12-24Add support for changing the `diff` command via an environment variableAdrian Kummerlaender
While the file arguments remain fixed the actual `diff` application and its output style can be changed using the `CHANGE_LOG_DIFF_CMD` environment variable.
2015-12-24Remove unnecessary headersAdrian Kummerlaender
2015-12-24Remove `exit` logging and interpositionAdrian Kummerlaender
The library is designed to track the file changes performed by a single process, i.e. there is no need for explicitly stating when the process has exited. Furthermore this reduces the set of function interpositions to the ones handled by the `get_actual_function` method template.
2015-12-24Match namespace and directory structureAdrian Kummerlaender
2015-12-23Implement file change tracking using `diff`Adrian Kummerlaender
The newly introduced `ChangeTracker` class is now keeping track of all tracked file in addition to spawning and managing a corresponding `diff` instance that enables printing pretty _patch-style_ change summaries to the logging target. This commit introduces `boost-process` and `diff` as dependencies of this library.
2015-12-21Add file mode check in `unlink`Adrian Kummerlaender
2015-11-30Extract actual function acquisitionAdrian Kummerlaender
The pointers to the actual function implementations are now fetched inside the `actual` namespace declared in the `actual_function.h` header. Fixed source of _noreturn_ related warning during compilation by adding the appropriate flag. Sadly this means that we can not use `std::function` in this context as it doesn't seem to carry these _c-like_ flags.
2015-11-14Fix rename tracking and enable logfile creationAdrian Kummerlaender
2015-10-18Implement logging of writable `mmap` creationsAdrian Kummerlaender
2015-10-18Add cmake build instructionsAdrian Kummerlaender