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On modern operating systems, memory management is non-deterministic (i.e. random, unpredictable) to varying degrees. This makes testing for memory leaks a nightmare as the OS may decide to randomly grow a process's memory allocation at any time for no apparent reason, causing intermittent test failures that do not represent real memory leaks. So far, the leaks test tried to cope with this by using a large number of iterations plus a certain amount of bytes of tolerance per iteration. This was inefficient and on some systems still did not fully eliminate intermittent test failures. This commit introduces a new testing algorithm that is designed to cope with a large degree of unpredictability. Instead of a fixed number of test iterations, it defines a maximum (16384), dividing them in blocks of 128 iterations. It also defines a minimum number of sequential "good" iteration blocks, counted if memory usage did not increase from one block to the next. That minimum number is set to 16. The theory is that if we can get 16 "good" iteration blocks in a row, we can safely assume it's not a real memory leak, break the loop, and consider the test succeeded. That "good" sequence is allowed to occur at any point in the loop, creating a high built-in tolerance for non-deterministic shenanigans. It also speeds up the tests, as successful tests can bow out at 16 * 128 == 2048 iterations if they're lucky. If the OS decides to randomly grow the memory heap, it may take more tries, but almost (?) certainly not more than the maximum 16384 (128 blocks). If the counter reaches that, then we assume a memory leak and throw a test failure. We're also no longer testing with byte granularity in any case; the randomness of memory management makes that pointless. All getmem() function versions now return kibibytes (1024 bytes). This should eliminate the need for workarounds such as initial iterations to "steady the state" or a tolerance of a certain number of bytes. I've experimentally determined the exact values (max_iter, block_iter, min_good_blocks) that seem to work reliably on all systems I've tested. They are easy to tweak if necessary. To make all this manageable, this commit hides all the supporting code in a triplet of aliases (TEST, DO, DONE) that, when used correctly, create a grammatically robust shell code block: you can add redirections, pipe into it, etc. as expected. This makes the actual tests a great deal easier to read as well. src/cmd/ksh93/tests/pty.sh: - Implement new leaks testing framework as described and convert all the tests to it. - Mark known leaks with a 'known' variable. Print non-fail warnings for all known leaks, but skip the tests by default. Test them only if DEBUG is exported. This is better than commenting them out as we will no longer be tempted to forget about these. - Move the test for large command substitutions to subshell.sh -- it's not in fact a leak test; instead, it checks that command substitutions don't lose data. src/cmd/ksh93/tests/_common: err_exit(): - Since we're printing more warnings, clearly mark all test failures with 'FAIL:' to make them stand out. src/cmd/ksh93/tests/shtests. src/cmd/ksh93/tests/pty.sh: - Special-case leaks.sh for counting tests; grep ^TEST. - Special-case pty.sh as well while we're at it by grepping tst() calls. Remove all the dummy '# err_exit #' comments from pty.sh as they are now no longer used for counting the tests.
41 lines
1.7 KiB
Text
41 lines
1.7 KiB
Text
########################################################################
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# #
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# This file is part of the ksh 93u+m package #
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# Copyright (c) 1982-2012 AT&T Intellectual Property #
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# Copyright (c) 2021 Contributors to ksh 93u+m #
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# <https://github.com/ksh93/ksh> #
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# and is licensed under the #
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# Eclipse Public License, Version 1.0 #
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# #
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# A copy of the License is available at #
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# http://www.eclipse.org/org/documents/epl-v10.html #
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# (with md5 checksum b35adb5213ca9657e911e9befb180842) #
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# #
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# Martijn Dekker <martijn@inlv.org> #
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# #
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########################################################################
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_message()
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{
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print -r $'\t'"${Command}[$1]: ${@:2}" >&2
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}
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function err_exit
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{
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_message "$1" "FAIL:" "${@:2}"
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let Errors+=1
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}
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alias err_exit='err_exit $LINENO' # inaccurate err_exit name kept for historical integrity :)
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alias warning='_message "$LINENO" "warning:"'
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Command=${0##*/}
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integer Errors=0
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if [[ -o xtrace ]]
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then # PS4 is set and exported in shtests
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typeset -F SECONDS # show fractional seconds in xtrace output
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fi
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if ! [[ -d $tmp && -w $tmp && $tmp == "$PWD" ]]
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then print -r "$Command: \$tmp not set; run this from shtests. Aborting." >&2
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exit 1
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fi
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