质控/二进制二分查找(Bibisect)

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简介

二进制二分查找(Bibisect,即 "binary bisect"),是一整套在软件中定位导致了某项功能“倒退(regressions)”的源代码提交(commit)的方法。“倒退”问题是软件开发以及质量控制中最应该避免的错误,它是指在原来的版本中表现完好的某项功能,在后续的版本中却突然无法使用或者无法正常工作的现象,这通常是由于在之前能正常工作的版本与最近不能正常工作的版本之间,存在一个或多个有缺陷的源代码提交。我们需要尽早发现“倒退”问题,并尽快定位导致该问题的有缺陷的源代码,这是因为在问题出现的早期通常会很容易定位该问题,而时间过的越旧,查找它就会越困难。

Bibisect 二进制二分查找原理

每个 bibisect 软件包(或者称为 bibisect 仓库)其实都是一个 git 仓库,该仓库中包含了成百上千个(次)从源代码编译的 LibreOffice 二进制程序,这些二进制程序在放入该 git 仓库时是按照对应的源代码提交先后顺序排列的。按照这种方式组织的 LibreOffice 二进制包的集合,是我们在多个版本中定位导致某个“倒退”问题源代码的绝佳方式。有了 bibisect 仓库,我们在测试时不需要每次切换到某个版本之后运行程序时重新编译源代码了。

采用这种方式,我们一方面可以使用 git 本身的二分查找工具(即 git bisect)直接基于二进制程序进行二分查找,另一方面又能受益于 git 对文件系统良好的差分压缩、去重以及文件组织方式。例如,一次完整的 LibreOffice 源代码编译后生成的二进制可执行程序至少会占用500MB磁盘空间,但是如果采用 git, 则虽然第一次添加占用的空间相同,但是后续每次添加产生的增量磁盘空间可能只有 25MB 大小。

您可以观看一部 Youtube 视频(墙外): Effective Bisection and Bibisection (Matthew Francis 于2015年在LibOCon上的演讲),它介绍并实际演示了使用 bibisect 仓库进行二进制二分查找的过程。

详情

一次成功的“二进制二分查找”(bibisect)会将导致“倒退”问题的可能源代码范围缩小至很少的几个commit,开发者可以从这个小范围内迅速找到引起“倒退”问题的真正“罪魁祸首”。 Bibisect 之后,QA 团队可以进行额外的步骤进行 bisect,从而将范围缩小到某个具体的源代码 commit, 或者将这项任务留给开发者完成。通常情况下,只要进行了成功的 bibisect, 则找到具体的导致“倒退”问题的具体 commit 会非常容易。

使用不到 10G 的 bibisect 仓库,您可以用于成百上千个编译后的 LibreOffice 版本进行测试。通常情况下完成一个 bibisect 二分查找过程只需要不到15分钟。

当前,“二进制二分查找”可在以下操作系统上进行:

涵盖的源代码范围及构建数章节所示, 取决于您所用的 bibisect 仓库,其涵盖的源代码 commit 范围,对于类似“43max”这样的仓库可能是80个一次构建(某些仓库可能达到几百个);而对于比较新的仓库,可能每隔1个或2个 commit 就有一次构建。(还有一些比较“粗糙”的仓库只是对每次的已发布版本 + beta 版本 + RC 版本进行了构建,这些仓库可能每个二进制构建涵盖上百个源代码 commit)。

当找到了commit范围后,您所测试的 bug 就可以标记关键词 "bibisected";进一步,如果找到了具体的 commit 之后,就可以再添加 "bisected" 关键词。

一般性说明

对于初学者,我们建议大家从已经完成了 bibisect 过程的示例中进行学习。为此,我们准备了Bibisect 入门教程

注意:二分查找的过程在不同的操作系统下会有差异。请阅读上面的链接中针对您的操作系统的指南,那里有非常详细的解释说明、视频以及其他资料。

“二进制二分查找”仅需要6个简单的步骤即可完成:

  1. 搭建环境,包括安装必要的软件。
  2. 下载 bibisect 仓库(其实质是集合了很多 LibreOffice 二进制包的 git 仓库,仓库中的每个commit对应的对 LibreOffice 源代码的一次编译)。
  3. 使用该 bibisect 仓库对 bug 进行二分查找。
  4. 获得二分查找的日志。
  5. 将日志附加到 bug 报告中。
  6. 更新 bug 报告的相应字段。
  7. 移除 keyword 字段中的 'bibisectRequest' 关键词,并添加 'bibisected' 关键词。
  8. 如果已经知道了究竟是哪个 commit 导致了问题,请同时添加 'bisected' 关键词,并将对应的开发者添加到 CC 列表中,并添加评论:'Adding Cc: to <开发者的名字>'

需要注意的是,您应当将最初的代码提交者(committer)添加到 CC 列表,而不是审阅者(Reviewer)。如果某个开发者已经不再参与这个项目了(您可以检查他/她最后一次提交commit的日期来判断),那么就没有必要将任何人添加到 CC 列表,此时您应当提高这个 bug 的优先级。

Some bibisect repositories have ranges of source commits folded into a single chunk. If after completing a bibisect you are presented with only a single one of these chunk commits, you can get the range by first copying the hash (note: not the source hash) and using it in a git log command like so:

git log c3f9dc54188b316a61dd871b63734d49b05f5d7f

现在,您可以复制第一个和前一个显示的二进制 commit 对应的源代码散列值(source hash),并构造出类似下面的查询: https://git.libreoffice.org/core/log/7c4d3ea6ba4d42b4dda5148a00c8c411b5d7703d..5b195fbcf7a441aeb193f6abd08b877e580938e0 得到这个范围之后,您就能通过范围内源代码 commit 的描述和变化内容来进行更深层次的筛查。见:深层次筛查部分的内容

限制

要进行 bibisect,您必须已经下载了针对您的操作系统的二进制软件 git 仓库,并且该仓库覆盖了合适的 LibreOffice 源代码 commit 范围。在这方面,我们在 GNU/Linux 操作系统下覆盖很全面。我们正在努力完善 Windows 和 macOS 下的覆盖度。

Some regressions are difficult to reproduce, and may require multiple test runs for a bug to appear. As you may imagine, trying to bibisect such regressions is very difficult, and requires one to perform many test runs after each checkout of a new version of LibreOffice to give some security / statistics that the bug is indeed present or not present with the given version.

我们当前不支持以下平台上的 bibisect:

版本

Bibisect 仓库的版本包含在了不同的操作系统相关的介绍里,请见上面的 #详情 部分。

无法进行 Bibisect 的 bug

有一些 bug 无法进行 Bibisect,这包括:

  • Bugs that don't show up on a supported platform (see #Limitations)
  • Bugs that predate our bibisect builds (We're working on extending the range covered)
  • Bugs that depend upon build options not enabled in the TDF builds (e.g. -kde)

If a bug with bibisectRequest Keyword is found to be not bibisectable, leave a comment on the bug explaining why we're not able to use bibisect to track down the introduction of this problem, and replace Keyword bibisectRequest with notBibisectable. If a bug predates bibisect builds, replace Keyword bibisectRequest with preBibisect.

找到 bug

找到需要进行“二进制二分查找”的 bug

以下 bug 包含 bibisectRequest 关键字,需要进行二进制二分查找:

另外,二进制二分查找对于解决LibreOffice中所有未解决的倒退性问题均会有帮助。

找到已经完成了“二进制二分查找”的 bug

请见 这里.

加入以上信息之后,开发者会知道这个“倒退”问题是在 master 分支源代码提交的 fb754a0df859e30255c25af8fa19bfaa75f257e7 (好) 和 2d19e9bb07ccff3134f855812dddfda5c07b1fe4 (坏) 之间产生的。

git log fb754a0df859e30255c25af8fa19bfaa75f257e7..2d19e9bb07ccff3134f855812dddfda5c07b1fe4

以上 git 命令将会显示 128 个提交,其中就包含了造成倒退问题的那个 bug. 这样,开发者就离修复这个 bug 不远了。 更多信息,请参考:

特殊情况

二分查找与特定语言(比如中日韩语言界面)相关的 bug

您要二分查找的 bug 可能与特定的界面语言相关。比如 tdf#115637,这个 bug 在中文界面上能够100%出现,而在英文界面上从来不出现。在这种情况下,因为 TDF 提供的二分查找仓库中默认没有提供任何语言包,只有英文界面,因此如果不进行改进,就无法二分查找这样的 bug。

如果某个 bug 在英文界面上工作正常,但在非英文界面上有问题(例如中日韩界面),您可以将以下文件从一个包含您的界面语言的常规发布版本中,复制到 bibisect 仓库:

  1. program/resource/<您的语言标记>
  2. share/registry/Langpack-<您的语言标记>.xcd
  3. share/registry/res/fcfg_langpack_<您的语言标记>.xcd
  4. share/registry/res/registry_<您的语言标记>.xcd

复制时,请注意尽量复制主版本号相同的版本中的资源。比如,对于 bibisect-linux-64-6.0 仓库,您可以复制 6.0.1.1 版本中的语言资源。

以单独的“用户配置文件”运行程序

如果想将用户配置文件放到 /tmp/ 临时目录中(该目录下的所有内容将在系统重启后被删除):

./opt/program/soffice -env:UserInstallation=file:///tmp/soffice-bisect

如果想在每次的二分查找中都让 libreoffice 以全新的用户配置文件启动,那么可以将 git commit 的希哈值附加到文件夹名称中,例如:

./opt/program/soffice \
-env:UserInstallation=file:///tmp/soffice-bisect-$(git rev-parse HEAD)

逆向 bibisect(找到修复了某个问题的提交)

Sometimes a bug is a collateral damage of another (possibly minor) bug, in a non obvious way. In such cases that other bug might be fixed on master, but was not backported to the release branch. To identify a problem-fixing commit you can use:

git bisect start --term-new=fixed --term-old=unfixed
git bisect fixed master
git bisect unfixed <some-old-sha> # you can use "git log --reverse" to detect the first revision in the bibisected package

As you test, say

git bisect fixed

or

git bisect unfixed

as appropriate.

If the fix is small and important enough, it likely can be easily backported to the release branch.

根据源代码的 hash 值检出某个特定的提交

有时候,您已经知道,在之前的某个特定的源代码 commit 中不存在您正在测试的 bug。

这种情况下,复制 LibreOffice 源代码 git 历史中的这个 source hash,并用它再 bibisecct 仓库的 log 中进行 grep:

git log --all --grep='29a9f433c268414747d8ec7343fc2b5987971738'

然后复制 bibisect 中的 commit hash,检出这个 commit,然后验证您的假设:

git checkout 38758b70f5278d4d8292a2e857e80a9a1130f38e

然后您可以使用 bibisect 仓库的 commit hash 来决定 bisect 过程中的 bad 和 good 的范围:

git bisect start 38758b70f5278d4d8292a2e857e80a9a1130f38e oldest

在某个 commit 范围内进行侦察

In case your bibisect result is a range of commits and you have trouble locating the offending commit, you might make your life easier by searching with a keyword.

An example for a case, where we know the problem is in Calc's Navigator view:

git log --stat --pretty=short --graph 169bd7718264b0e312052757f9bbd2321e1399c2...ff8b873936aa72b17309da4bfc2775573a5b1f55 | grep -B 10 -A 10 --color=always "sc/source/ui/navipi" | less -R

Adjust the -B and -A grep parameters to control how many lines before and after the hit you want to display. When piping to less, -R preserves the colouring of search results.

Bisect skip(跳过无法运行的 commit)

Sometimes we get stuck in a miserable situation, where we have to use git bisect skip over and over again due to various reasons. There are ways of getting out of these infuriating messes and here we will show one of them.

示例 bug: tdf#123095

Bug 出现在 4.0-4.1 范围内。

这里有太多的与自动筛选(autofilter)无关的 commit 了,因此需要忽略这些。

我们可以使用 git bisect visualize 来显示剩下的有嫌疑的 commits:

git bisect visualize --oneline > /some/path/bisect-viz-123095.txt

顶部显示的是最早的“坏”结果,底下显示的是您已经忽略的内容。再往下显示的是最近已知的“好”结果。

我的顶部结果包括:

  b842ac1 source-hash-7b4d76772ef76a8de852ed647ed0cad368f70189
  40ef04e source-hash-dc173b7f2a550185404aacbc6da744cb6d1880fc
  8e697de source-hash-eb96e4325278f31b9e6fbc1d5c6a01543204ded6

因此,我进行 git checkout b842ac1,测试检出的程序,再继续下一个,重复这个步骤。看起来顶部的第三个是一个可以忽略的提交。

我使用 source hash 按照 bottomcommit..firstbadcommit 的方式构造了一个查询

打开查询界面后,我进而搜索 "filter",然后找到了一个可疑的 commit,这个提交是关于对自动筛选的结果进行排序的。

如果在 bibisect 过程中 soffice 在某个或某几个 commit 下频繁崩溃,让您无法准确判断代码范围,那么 #Tidbits for efficiency 章节提供了解决办法。

使用 bibisect 找到源代码 commit

If bibisect was done, but not likely to be correct or in a repository known to have large range of source commits, we can check the range by finding a previous build commit from the found one and then find the source range.

$ git log -1 1f14665c5624bc7a502738aa8f4f2bd70a211e72^
$ git log --oneline b6c016da23d309b4ac7d154bc33a22397974ed73..d85fd8a85501547d5bb87822d2589a07aed7f2d6

故障排除

Please add your problems and how you solved them. This section covers issues that affect more than one OS. For OS-specific issues, please see the individual OS wiki pages.

无法提取文件

If you can't extract files (you should get an error message). Try to rename the file from *.tar.lzma to *.tar.xz.

已安装的 LibreOffice 被意外修改

问题 / 信息:

   error: Your local changes to the following files would be overwritten by checkout:
     opt/program/pythonloader.pyc
     opt/program/uno.pyc
     opt/program/unohelper.pyc
   Please, commit your changes or stash them before you can switch branches.
   Aborting

解决办法:

git checkout .

The above command will repair the problem. Afterwards you can start the next test run as usual with

git bisect good # or git bisect bad

If that does not solve the problem, you can try the following commands:

git clean -fd
git reset --hard

The ultimate repair is to delete everything except one hidden .git/ folder,

and do

git checkout oldest

无法启动 soffice

Problem 1: Upon trying to run soffice within bibisect you receive the error "unexpected operator terminate called after throwing an instance of 'com::sun::star::uno::DeploymentException'

Solution: Reset your libreoffice profile located in ~/.config/libreoffice. Make sure to backup the folder if you have any settings you'd like to preserve for use with your stable libreoffice release. After you're done with bibisect you can try to return your backed up profile to it's original location (ie. delete the new profile folder and replace it with the backed up one)

Problem 2: Trying to run soffice within bibisect gives frequent errors such as "Application Error" and skipping via 'git bisect skip' is tedious.

Solution: Upon an error, run one-line script to skip commit on error message and try the next one. Script will stop when soffice is successfully run and then you proceed with 'git bisect good' or 'git bisect bad'. If error is repeated, script can be run again.

 while (git clean -f -X && git bisect skip && ! instdir/program/soffice); do : ; done

如果 bisect RTL(从右向左)类型的 bug

如果想要对 RTL ( Right-To-Left,从右向左) 语言相关的 bug, 在运行 LibreOffice 之前请导入如下的变量:

SAL_RTL_ENABLED=1

如何 bisect 文件恢复类型的 bug

In case you need to bisect File Recovery bugs ( e.g. tdf#129210 ), comment out line OOO_DISABLE_RECOVERY=1 in file instdir/program/ooenv

You may also use user control:

soffice --norestore file-that-recovers.ext

How to bisect file hanging / CPU or memory exhaustion bugs

In case you need to bisect file hanging/memory exhaustion bugs, you may limit memory or CPU or time execution.

In Linux, timeout utility can be used. To avoid confusion with built-in "timeout" command, here it's renamed to "tmt".

For example, if LibreOffice 'good' commit opens a file with 1 GB of memory, you may set soffice memory limit to 1.500.000 kilobytes to avoid 'bad' commit hanging your computer.

tmt -m 1500000 instdir/program/soffice

Or, to limit CPU+SYS time (where normal time is seen with successful run):

tmt -t 20 instdir/program/soffice

More advanced option is to use benchexec utility. User needs to be added to the appropriate group (benchexec). Runexec can be used to execute a single command while measuring its resource consumption, similarly to the tool "time" but with more reliable time measurements and with measurement of memory usage.

In Windows, process-governor utility can be used.

提高效率

The repetitive nature of bibisecting gets tedious fast, so every trick you can use to make the process quicker is valuable. A typical way is to define aliases for complex commands in your .bashrc file.

The .bashrc of an active bibisecter might include a block such as this:

alias bad='git bisect bad && instdir/program/soffice'
alias good='git bisect good && instdir/program/soffice'
alias skip='git bisect skip && instdir/program/soffice'
alias next='git log --reverse --pretty=%H master | grep -A 1 $(git rev-parse HEAD) | tail -n1 | xargs git checkout'
alias prev='git checkout HEAD^1'
alias gallery='rm instdir/program/gengal'
alias pycache='find . | grep -E "(__pycache__|\.pyc|\.pyo$)" | xargs rm -rf'
alias source='if [[ $(git log -1) =~ sha:([[:alnum:]]+) ]]; then git --git-dir ~/libreoffice/.git log -1 ${BASH_REMATCH[1]}; fi'
alias sof="\$( if [[ -d instdir ]] ; then echo instdir ; else if [[ -d opt ]] ; then echo opt ; fi ; fi )/program/soffice --norestore --nologo"

We have commands for jumping to the next or previous commit, "pycache" for dealing with a Windows-specific annoyance and finally "source" for quickly displaying source commit information. The command named "source" assumes you are in a bibisect repository, grabs the source hash of the currently checked out commit and feeds it to a git command targeting a full clone of the LibreOffice source code. To get a breakdown of the command, see the Bash Reference Manual. "sof" introduces single command for newer repos with instdir and older with opt directories.

The above examples are not exclusive to *nix systems, but work fine in a cygwin environment on Windows. If you want to open documents from the cygwin command line, enclose the ordinary Windows path in single quotes like so: instdir/program/soffice 'c:\users\test\downloads\example.ods'

Another approach would be to assume one will also do reverse bibisects, so use "before" and "after" instead of "good" and "bad". soffice command remains separate and can be replaced with "sof" and combined with "gen" or "skia". "skip" is useful when LO doesn't start, but it can also be temporarily modified when a specific file cannot be loaded. "loexit" is used with "time" to measure loading time with auto exit.

alias gbs='echo "git bisect start master oldest" && git bisect start master oldest'
alias gbb='echo "git bisect before" && git bisect good'
alias gba='echo "git bisect after" && git bisect bad'
alias skip='while (git clean -f -X && git bisect skip && ! (SAL_USE_VCLPLUGIN=gen instdir/program/soffice)); do : ; done'	
alias gen='SAL_USE_VCLPLUGIN=gen'
alias skia='SAL_ENABLESKIA=1 SAL_USE_VCLPLUGIN=gen'
alias loexit='OOO_EXIT_POST_STARTUP=1'
alias buildc='lynx https://git.libreoffice.org/core/+log/`instdir/program/soffice   --version |  awk '"'"'{print $(NF)}'"'"'`  ' 
build() { lynx https://git.libreoffice.org/core/+log/"$1"; }
log() { git log --all --grep="$1"; }

Alias "buildc" opens web page with current commit, showing it's time and author. Function "build" opens master , while "build d376297c643785564e7bda1a74b573c35ade6cb8" checks the specific commit. Function "log 3678e0efcb8bedc58dd329a430da0ac3b1572df8" finds bisect commit of source commit in current repo.

For example, with those commands one can bibisect change in fileopen time, inlcuding in old versions, as:

gbs && time loexit gen sof file.ext.

更多信息

备注

Bibisect 仓库是如何生成的:

We want to make a GUI for bibisect: