【问题标题】：`nix-build` fails because Python wants something that's unavailable, without saying what it wants`nix-build` 失败是因为 Python 想要一些不可用的东西，但没有说它想要什么
【发布时间】：2020-01-28 07:10:13
【问题描述】：

（至少我认为这是问题所在。）

错误

当我从 nixpkgs 的根目录运行 nix-build -A serialosc 时，nix 会打印以下内容：

[jeff@jbb-dell:~/nix/nixpkgs-fork]$ nix-build -A serialosc
these derivations will be built:
  /nix/store/p40wvn28grb8nrcd6scbxhhjqw4495kk-serialosc.drv
building '/nix/store/p40wvn28grb8nrcd6scbxhhjqw4495kk-serialosc.drv'...
unpacking sources
unpacking source archive /nix/store/5zj802wfjd0ima92lpzzsqdjqvrnrwf9-serialosc
source root is serialosc
patching sources
configuring
configure flags: --prefix=/nix/store/b6qzvzmwjdi29nnzc769904wc0mj1cds-serialosc configure
Setting top to                           : /build/serialosc 
Setting out to                           : /build/serialosc/build 

Checking for 'gcc' (C compiler)          : gcc 

Checking for working poll()              : yes 
Checking for libudev                     : yes 
Checking for libmonome                   : yes 
Checking for liblo                       : yes 
Checking for function strdup             : yes 
Checking for function _strdup            : not found 
Checking for function strndup            : yes 
Checking for function strcasecmp         : yes 
Checking for header unistd.h             : yes 
Checking for header dns_sd.h             : yes 
Checking for library dl                  : yes 

Traceback (most recent call last):
  File "/build/serialosc/.waf-1.8.5-3fc7b0f5070c04bfd3f2489448471a84/waflib/Scripting.py", line 103, in waf_entry_point
    run_commands()
  File "/build/serialosc/.waf-1.8.5-3fc7b0f5070c04bfd3f2489448471a84/waflib/Scripting.py", line 164, in run_commands
    ctx=run_command(cmd_name)
  File "/build/serialosc/.waf-1.8.5-3fc7b0f5070c04bfd3f2489448471a84/waflib/Scripting.py", line 155, in run_command
    ctx.execute()
  File "/build/serialosc/.waf-1.8.5-3fc7b0f5070c04bfd3f2489448471a84/waflib/Configure.py", line 92, in execute
    super(ConfigurationContext,self).execute()
  File "/build/serialosc/.waf-1.8.5-3fc7b0f5070c04bfd3f2489448471a84/waflib/Context.py", line 92, in execute
    self.recurse([os.path.dirname(g_module.root_path)])
  File "/build/serialosc/.waf-1.8.5-3fc7b0f5070c04bfd3f2489448471a84/waflib/Context.py", line 133, in recurse
    user_function(self)
  File "/build/serialosc/wscript", line 259, in configure
    stderr=devnull).decode().strip()
  File "/nix/store/lbrpma3528hq7gwn8ffbnwaxvsqah0bb-python-2.7.17/lib/python2.7/subprocess.py", line 216, in check_output
    process = Popen(stdout=PIPE, *popenargs, **kwargs)
  File "/nix/store/lbrpma3528hq7gwn8ffbnwaxvsqah0bb-python-2.7.17/lib/python2.7/subprocess.py", line 394, in __init__
    errread, errwrite)
  File "/nix/store/lbrpma3528hq7gwn8ffbnwaxvsqah0bb-python-2.7.17/lib/python2.7/subprocess.py", line 1047, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
builder for '/nix/store/p40wvn28grb8nrcd6scbxhhjqw4495kk-serialosc.drv' failed with exit code 2
error: build of '/nix/store/p40wvn28grb8nrcd6scbxhhjqw4495kk-serialosc.drv' failed

[jeff@jbb-dell:~/nix/nixpkgs-fork]$

我的怀疑

问题似乎出现在lib/python2.7/subprocess.py。我在网上找到了a version of that file，而definition of _execute_child 似乎引用了一些绝对路径——例如，在这段话中：

    if shell:
        args = ["/bin/sh", "-c"] + args
        if executable:
            args[0] = executable

因此，我的猜测是 Nix 是在一个沙盒中构建的，它不提供 Python 所期望的任何东西。但错误并没有告诉我 Python 希望找到什么。

上下文

（您可能不需要此信息。）

我正在尝试在 NixOS 19.09 上build serialosc。这是我的fork of nixpkgs，包括我的broken recipe for serialosc。这个分支还包括我的libmonome 包，它可以工作，serialosc 依赖于它，它还不是官方nixpkgs 存储库的一部分。我已经给出了具体提交的硬链接；当我更新分叉时，它们不应该改变。

【问题讨论】：

就个人而言，我会通过使用 sysdig 来跟踪失败的execve() 调用试图调用什么来调试它。（在 NixOS 上，您可能需要小心使用哪个内核包——至少有一段时间，sysdig 无法使用 nixpkgs 中的默认内核构建；但希望现在已经修复，如果上游没有修复，它在任何情况下都是可修复的）。

标签： python-2.7 sandbox nix nixos

【解决方案1】：

交叉发布自 https://discourse.nixos.org/t/nix-build-fails-because-python-wants-something-thats-unavailable-without-saying-what-it-wants/5675/2 所以它可以帮助那些只找到这个的人，答案可能会在 NixOS 的话语中继续。我试图让它对一般的 NixOS 编写派生调试有所帮助，并带有一些 Python 位

fetchgit

首先，让我们帮助您解决食谱中的 fetchgit 部分

  src = fetchgit {
    # Once, it seemed to finish, and I don't know how! Then it crashed with:
    # Switched to a new branch 'fetchgit'
    # removing `.git'...
    # hash mismatch in fixed-output derivation '/nix/store/5zj802wfjd0ima92lpzzsqdjqvrnrwf9-serialosc':
    # wanted: sha256:1vqcxi32wc4pklbddllflkaigkfvd4ykwrjqccayvrk10dx1sna3
    # got:    sha256:1zmzjasv21ix7i7s58a31k0025ji32hv2jm2ww6s0xhjmr5ax34j

    # This way it [[gets pretty far]].
    # The fetchSubmodules value I set again seems to have no effect.
    url = https://github.com/monome/serialosc.git;
    rev = "v1.4.1";
    sha256 = "1zmzjasv21ix7i7s58a31k0025ji32hv2jm2ww6s0xhjmr5ax34j";

也许有强制推动？不知道为什么它会停止使用哈希

我发现 fetchSubmodules 没有任何效果，如果你有没有子模块的哈希，请使用 nix-prefetch-git --fetch-submodules https://github.com/monome/serialosc 给出

{
  "url": "https://github.com/monome/serialosc",
  "rev": "cec0ea76b2d5f69afa74d3ffc14a0950e32a7914",
  "date": "2019-06-09T21:46:13+02:00",
  "sha256": "03qkzslhih72idwafgfxmkwp5v3x048njh0c682phw2ks11plmbp",
  "fetchSubmodules": true
}

所以用

fetchgit {
  url = https://github.com/monome/serialosc;
  rev = "cec0ea76b2d5f69afa74d3ffc14a0950e32a7914";
  # or rev = version; but that might break with force pushes
  sha256 = "03qkzslhih72idwafgfxmkwp5v3x048njh0c682phw2ks11plmbp";
  fetchSubmodules = true;
}

wafHook

https://nixos.org/nixpkgs/manual/ 中有一个（少量）wafHook 文档

调试错误

它似乎想做git的东西，这是我调试它的方式：

$ nix-shell https://github.com/JeffreyBenjaminBrown/nixpkgs/archive/2bbd131811991bec9ae6b296b5cd1441640c306c.tar.gz -A serialosc --pure
nix-shell $ mkdir /tmp/delme-serialosc
nix-shell $ cd !$
# To find out what a build would do
nix-shell $ type genericBuild
...
# Doing the `if [ -z "${phases:-}" ]; then ...` bit gives us `echo $phases`
# unpackPhase patchPhase configurePhase buildPhase checkPhase installPhase fixupPhase installCheckPhase distPhase
nix-shell $ ${unpackPhase:-unpackPhase}
nix-shell $ cd $sourceRoot
nix-shell $ ${patchPhase:-patchPhase}
nix-shell $ ${configurePhase:-configurePhase}
# Error happens here
nix-shell $ type ${configurePhase:-configurePhase}
# Do the steps until you find it stops in `python ...`
# Python debug info: https://docs.python.org/3/library/pdb.html
nix-shell $ python -m pdb "$wafPath" "${flagsArray[@]}";
(Pdb) continue # or cont, or just c
...
(Pdb)  break /nix/store/lbrpma3528hq7gwn8ffbnwaxvsqah0bb-python-2.7.17/lib/python2.7/subprocess.py:1047
(Pdb) continue
> /nix/store/lbrpma3528hq7gwn8ffbnwaxvsqah0bb-python-2.7.17/lib/python2.7/subprocess.py(1047)_execute_child()
-> raise child_exception
(Pdb) up 
> /nix/store/lbrpma3528hq7gwn8ffbnwaxvsqah0bb-python-2.7.17/lib/python2.7/subprocess.py(394)__init__()
-> errread, errwrite)
(Pdb) # empty is equivalent to do last command, i.e. up in this case
> /nix/store/lbrpma3528hq7gwn8ffbnwaxvsqah0bb-python-2.7.17/lib/python2.7/subprocess.py(216)check_output()
-> process = Popen(stdout=PIPE, *popenargs, **kwargs)
(Pdb) print(popenargs)
(['git', 'rev-parse', '--verify', '--short', 'HEAD'],)

但是您会发现您可能需要想办法避免使用waf 使用git，因为它无法访问网络，除非它是一个固定输出派生（例如那些获取源）。希望关于fetchSubmodules 的内容能够解决它！

编辑：我没有读过它试图使用 git，它试图找出它是什么版本，你应该以某种方式让它避免使用 git 来做到这一点，例如grep -r 'rev-parse' 建议编辑 wscript 文件

编辑 2：例如像

--- wscript-old 2020-01-29 15:55:54.100976818 +0000
+++ wscript     2020-01-29 15:55:58.128977024 +0000
@@ -257,7 +257,7 @@
                conf.env.GIT_COMMIT = subprocess.check_output(
                        ["git", "rev-parse", "--verify", "--short", "HEAD"],
                        stderr=devnull).decode().strip()
-       except subprocess.CalledProcessError:
+       except (subprocess.CalledProcessError, OSError):
                conf.env.GIT_COMMIT = ''

        conf.define("VERSION", VERSION)

也许它也可以被上游化（在这种情况下，这会使 git commit ID 为空）？或者只是使用substituteInPlace 或其他东西来输入实际的提交ID

--- wscript-old 2020-01-29 15:55:54.100976818 +0000
+++ wscript     2020-01-29 15:57:56.177983054 +0000
@@ -249,16 +249,7 @@

        conf.env.VERSION = VERSION

-       try:
-               import os
-
-               devnull = open(os.devnull, 'w')
-
-               conf.env.GIT_COMMIT = subprocess.check_output(
-                       ["git", "rev-parse", "--verify", "--short", "HEAD"],
-                       stderr=devnull).decode().strip()
-       except subprocess.CalledProcessError:
-               conf.env.GIT_COMMIT = ''
+        conf.env.GIT_COMMIT = 'cec0ea76b2d5f69afa74d3ffc14a0950e32a7914'

        conf.define("VERSION", VERSION)
        conf.define("_GNU_SOURCE", 1)

【讨论】：