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Essentially, the problem is that safemalloc is excruciatingly slow as it checks all allocated blocks for overrun at each memory management primitive, yielding a almost exponential slowdown for the memory management functions (malloc, realloc, free). The overrun check basically consists of verifying some bytes of a block for certain magic keys, which catches some simple forms of overrun. Another minor problem is violation of aliasing rules and that its own internal list of blocks is prone to corruption. Another issue with safemalloc is rather the maintenance cost as the tool has a significant impact on the server code. Given the magnitude of memory debuggers available nowadays, especially those that are provided with the platform malloc implementation, maintenance of a in-house and largely obsolete memory debugger becomes a burden that is not worth the effort due to its slowness and lack of support for detecting more common forms of heap corruption. Since there are third-party tools that can provide the same functionality at a lower or comparable performance cost, the solution is to simply remove safemalloc. Third-party tools can provide the same functionality at a lower or comparable performance cost. The removal of safemalloc also allows a simplification of the malloc wrappers, removing quite a bit of kludge: redefinition of my_malloc, my_free and the removal of the unused second argument of my_free. Since free() always check whether the supplied pointer is null, redudant checks are also removed. Also, this patch adds unit testing for my_malloc and moves my_realloc implementation into the same file as the other memory allocation primitives. client/mysqldump.c: Pass my_free directly as its signature is compatible with the callback type -- which wasn't the case for free_table_ent. |
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| .. | ||
| examples | ||
| mysys | ||
| mytap | ||
| Makefile.am | ||
| README.txt | ||
| unit.pl | ||
Unit tests directory structure
------------------------------
This is the current structure of the unit tests. More directories
will be added over time.
mytap Source for the MyTAP library
mysys Tests for mysys components
bitmap-t.c Unit test for MY_BITMAP
base64-t.c Unit test for base64 encoding functions
examples Example unit tests.
core-t.c Example of raising a signal in the middle of the test
THIS TEST WILL STOP ALL FURTHER TESTING!
simple-t.c Example of a standard TAP unit test
skip-t.c Example where some test points are skipped
skip_all-t.c Example of a test where the entire test is skipped
todo-t.c Example where test contain test points that are TODO
no_plan-t.c Example of a test with no plan (avoid this)
Executing unit tests
--------------------
To make and execute all unit tests in the directory:
make test
Observe that the tests in the examples/ directory are just various
examples of tests and are not expected to pass.
Adding unit tests
-----------------
Add a file with a name of the format "foo-t.c" to the appropriate
directory and add the following to the Makefile.am in that directory
(where ... denotes stuff already there):
noinst_PROGRAMS = ... foo-t
Note, it's important to have "-t" at the end of the filename, otherwise the
test won't be executed by 'make test' !
Documentation
-------------
The generated documentation is temporarily placed at:
http://www.kindahl.net/mytap/doc/
I will move it to a better place once I figure out where and how.