3. Using the autotools element

In the last chapter we observed how the manual element works, allowing one to specify and run commands manually in the process of constructing an artifact.

In this chapter, we’ll go over a mostly automated build of a similar hello world example. We will observe how our configurations of the autotools element translate to configurations on the manual element, and observe how variable substitution works.


This example is distributed with BuildStream in the doc/examples/autotools subdirectory.

3.1. Overview

Instead of using the local source as we have been using in the previous examples, we’re going to use a tar source this time to obtain the automake release tarball directly from the upstream hosting.

In this example we’re going to build the example program included in the upstream automake tarball itself, and we’re going to use the automated autotools build element to do so.

3.2. Project structure

3.2.1. project.conf

# Unique project name
name: autotools

# Required BuildStream format version
format-version: 9

# Subdirectory where elements are stored
element-path: elements

# Define some aliases for the tarballs we download
  alpine: https://bst-integration-test-images.ams3.cdn.digitaloceanspaces.com/
  gnu: http://ftpmirror.gnu.org/gnu/automake/

Like the last project.conf, we’ve added another source alias for gnu, the location from which we’re going to download the automake tarball.

3.2.2. elements/base/alpine.bst and elements/base.bst

The alpine base and base stack element are defined in the same way as in the last chapter: Running commands.

3.2.3. elements/hello.bst

kind: autotools
description: |

    Hello world example from automake


  # The hello world example lives in the doc/amhello folder.
  # Set the %{command-subdir} variable to that location
  # and just have the autotools element run it's commands there.
  command-subdir: doc/amhello

- kind: tar
  url: gnu:automake-1.16.tar.gz
  ref: 80da43bb5665596ee389e6d8b64b4f122ea4b92a685b1dbd813cd1f0e0c2d83f

- base.bst

In this case, we haven’t touched the element’s config section at all, instead we just slightly override the bahavior of the autotools build element by overriding the command-subdir variable Looking at variables

Let’s take a moment and observe how element composition works with variables.

As the documentation mentions:

  • The initial settings of the project.conf variables are setup using BuildStream’s builtin defaults.
  • After this, your local project.conf may override some variables on a project wide basis. Those will in turn be overridden by any defaults provided by element classes, such as the variables set in the documentation of the autotools build element. The variables you set in your final <element.bst> element declarations, will have the final say on the value of a particular variable.
  • Finally, the variables, which may be composed of other variables, are resolved after all composition has taken place.

The variable we needed to override was command-subdir, which is an automatic variable provided by the BuildElement abstract class. This variable simply instructs the BuildElement in which subdirectory of the %{build-root} to run it’s commands in.

One can always display the resolved set of variables for a given element’s configuration using bst show:

user@host:~/autotools$ bst show --deps none --format "%{vars}" hello.bst

[--:--:--][][] STATUS  Cache usage recomputed: 12K / infinity (0%)
[--:--:--][][] START   Loading elements
[00:00:00][][] SUCCESS Loading elements
[--:--:--][][] START   Resolving elements
[00:00:00][][] SUCCESS Resolving elements
[--:--:--][][] START   Resolving cached state
[00:00:00][][] SUCCESS Resolving cached state
autogen: "export NOCONFIGURE=1;\n\nif [ -x ./configure ]; then true;\nelif [ -x autogen\
  \ ]; then ./autogen;\nelif [ -x autogen.sh ]; then ./autogen.sh;\nelif [ -x bootstrap\
  \ ]; then ./bootstrap;\nelif [ -x bootstrap.sh ]; then ./bootstrap.sh;\nelse autoreconf\
  \ -ivf;\nfi"
bindir: /usr/bin
build-root: /buildstream/autotools/hello.bst
command-subdir: doc/amhello
conf-args: "--prefix=/usr \\\n--exec-prefix=/usr \\\n--bindir=/usr/bin \\\n--sbindir=/usr/sbin\
  \ \\\n--sysconfdir=/etc \\\n--datadir=/usr/share \\\n--includedir=/usr/include \\\
  \n--libdir=/usr/lib \\\n--libexecdir=/usr/libexec \\\n--localstatedir=/var \\\n\
  --sharedstatedir=/usr/com \\\n--mandir=/usr/share/man \\\n--infodir=/usr/share/info"
conf-cmd: ./configure
conf-extra: ''
conf-global: ''
conf-local: ''
configure: "./configure --prefix=/usr \\\n--exec-prefix=/usr \\\n--bindir=/usr/bin\
  \ \\\n--sbindir=/usr/sbin \\\n--sysconfdir=/etc \\\n--datadir=/usr/share \\\n--includedir=/usr/include\
  \ \\\n--libdir=/usr/lib \\\n--libexecdir=/usr/libexec \\\n--localstatedir=/var \\\
  \n--sharedstatedir=/usr/com \\\n--mandir=/usr/share/man \\\n--infodir=/usr/share/info"
datadir: /usr/share
debugdir: /usr/lib/debug
docdir: /usr/share/doc
element-name: hello.bst
exec_prefix: /usr
fix-pyc-timestamps: "find \"/buildstream-install\" -name '*.pyc' -exec \\\n  dd if=/dev/zero\
  \ of={} bs=1 count=4 seek=4 conv=notrunc ';'"
includedir: /usr/include
infodir: /usr/share/info
install-root: /buildstream-install
lib: lib
libdir: /usr/lib
libexecdir: /usr/libexec
localstatedir: /var
make: make
make-install: make -j1 DESTDIR="/buildstream-install" install
mandir: /usr/share/man
max-jobs: '2'
objcopy-extract-args: --only-keep-debug --compress-debug-sections
objcopy-link-args: --add-gnu-debuglink
prefix: /usr
project-name: autotools
sbindir: /usr/sbin
sharedstatedir: /usr/com
strip-args: --remove-section=.comment --remove-section=.note --strip-unneeded
strip-binaries: "cd \"/buildstream-install\" && find -type f \\\n  '(' -perm -111\
  \ -o -name '*.so*' \\\n      -o -name '*.cmxs' -o -name '*.node' ')' \\\n  -exec\
  \ sh -ec \\\n  'read -n4 hdr <\"$1\" # check for elf header\n   if [ \"$hdr\" !=\
  \ \"$(printf \\\\x7fELF)\" ]; then\n       exit 0\n   fi\n   debugfile=\"/buildstream-install/usr/lib/debug/$1\"\
  \n   mkdir -p \"$(dirname \"$debugfile\")\"\n   objcopy --only-keep-debug --compress-debug-sections\
  \ \"$1\" \"$debugfile\"\n   chmod 644 \"$debugfile\"\n   strip --remove-section=.comment\
  \ --remove-section=.note --strip-unneeded \"$1\"\n   objcopy --add-gnu-debuglink\
  \ \"$debugfile\" \"$1\"' - {} ';'"
sysconfdir: /etc

As an exercise, we suggest that you modify the hello.bst element to set the prefix like so:

  prefix: "/opt"

And rerun the above bst show command to observe how this changes the output.

Observe where the variables are declared in the builtin defaults and autotools element documentation, and how overriding these affects the resolved set of variables.

3.3. Using the project

3.3.1. Build the hello.bst element

To build the project, run bst build in the following way:

user@host:~/autotools$ bst build hello.bst

[--:--:--][][] STATUS  Cache usage recomputed: 12K / infinity (0%)
[--:--:--][][] START   Build
[--:--:--][][] START   Loading elements
[00:00:00][][] SUCCESS Loading elements
[--:--:--][][] START   Resolving elements
[00:00:00][][] SUCCESS Resolving elements
[--:--:--][][] START   Resolving cached state
[00:00:00][][] SUCCESS Resolving cached state
[--:--:--][][] START   Checking sources
[00:00:00][][] SUCCESS Checking sources

BuildStream Version 1.4.2+20.g89765b75
  Session Start: Wednesday, 13-05-2020 at 10:41:01
  Project:       autotools (/home/user/autotools)
  Targets:       hello.bst
  Cache Usage:   12K / infinity (0%)

User Configuration
  Configuration File:      /home/user/.config/buildstream.conf
  Log Files:               /home/user/.cache/buildstream/logs
  Source Mirrors:          /home/user/.cache/buildstream/sources
  Build Area:              /home/user/.cache/buildstream/build
  Artifact Cache:          /home/user/.cache/buildstream/artifacts
  Strict Build Plan:       Yes
  Maximum Fetch Tasks:     10
  Maximum Build Tasks:     4
  Maximum Push Tasks:      4
  Maximum Network Retries: 2

   buildable d5472eb60ceb8a45b0ed5907912b5d89ce91d8a4e9b454ea2663f052c6cf4dff base/alpine.bst 
     waiting 50110d08831106135148d991c33f15794b530938712216e84593eeff7c1ef8ca base.bst 
     waiting 0713461b97fa9c6c4de17c3481d2b5f64fc51af435b0ce55e604283e913aa950 hello.bst 
[--:--:--][d5472eb6][build:base/alpine.bst               ] START   autotools/base-alpine/d5472eb6-build.1726.log
[--:--:--][d5472eb6][build:base/alpine.bst               ] START   Staging sources
[00:00:08][d5472eb6][build:base/alpine.bst               ] SUCCESS Staging sources
[--:--:--][d5472eb6][build:base/alpine.bst               ] START   Caching artifact
[00:00:04][d5472eb6][build:base/alpine.bst               ] SUCCESS Caching artifact
[00:00:14][d5472eb6][build:base/alpine.bst               ] SUCCESS autotools/base-alpine/d5472eb6-build.1726.log
[--:--:--][50110d08][build:base.bst                      ] START   autotools/base/50110d08-build.1728.log
[--:--:--][50110d08][build:base.bst                      ] START   Caching artifact
[00:00:00][50110d08][build:base.bst                      ] SUCCESS Caching artifact
[00:00:00][50110d08][build:base.bst                      ] SUCCESS autotools/base/50110d08-build.1728.log
[--:--:--][0713461b][build:hello.bst                     ] START   autotools/hello/0713461b-build.1730.log
[--:--:--][0713461b][build:hello.bst                     ] START   Staging dependencies
[00:00:01][0713461b][build:hello.bst                     ] SUCCESS Staging dependencies
[--:--:--][0713461b][build:hello.bst                     ] START   Integrating sandbox
[00:00:00][0713461b][build:hello.bst                     ] SUCCESS Integrating sandbox
[--:--:--][0713461b][build:hello.bst                     ] START   Staging sources
[00:00:00][0713461b][build:hello.bst                     ] SUCCESS Staging sources
[--:--:--][0713461b][build:hello.bst                     ] START   Running configure-commands
[--:--:--][0713461b][build:hello.bst                     ] STATUS  Running configure-commands

    export NOCONFIGURE=1;
    if [ -x ./configure ]; then true;
    elif [ -x autogen ]; then ./autogen;
    elif [ -x autogen.sh ]; then ./autogen.sh;
    elif [ -x bootstrap ]; then ./bootstrap;
    elif [ -x bootstrap.sh ]; then ./bootstrap.sh;
    else autoreconf -ivf;

[--:--:--][0713461b][build:hello.bst                     ] STATUS  Running configure-commands

    ./configure --prefix=/usr \
    --exec-prefix=/usr \
    --bindir=/usr/bin \
    --sbindir=/usr/sbin \
    --sysconfdir=/etc \
    --datadir=/usr/share \
    --includedir=/usr/include \
    --libdir=/usr/lib \
    --libexecdir=/usr/libexec \
    --localstatedir=/var \
    --sharedstatedir=/usr/com \
    --mandir=/usr/share/man \

[00:00:04][0713461b][build:hello.bst                     ] SUCCESS Running configure-commands
[--:--:--][0713461b][build:hello.bst                     ] START   Running build-commands
[--:--:--][0713461b][build:hello.bst                     ] STATUS  Running build-commands


[00:00:00][0713461b][build:hello.bst                     ] SUCCESS Running build-commands
[--:--:--][0713461b][build:hello.bst                     ] START   Running install-commands
[--:--:--][0713461b][build:hello.bst                     ] STATUS  Running install-commands

    make -j1 DESTDIR="/buildstream-install" install

[00:00:00][0713461b][build:hello.bst                     ] SUCCESS Running install-commands
[--:--:--][0713461b][build:hello.bst                     ] START   Running strip-commands
[--:--:--][0713461b][build:hello.bst                     ] STATUS  Running strip-commands

    cd "/buildstream-install" && find -type f \
      '(' -perm -111 -o -name '*.so*' \
          -o -name '*.cmxs' -o -name '*.node' ')' \
      -exec sh -ec \
      'read -n4 hdr <"$1" # check for elf header
       if [ "$hdr" != "$(printf \\x7fELF)" ]; then
           exit 0
       mkdir -p "$(dirname "$debugfile")"
       objcopy --only-keep-debug --compress-debug-sections "$1" "$debugfile"
       chmod 644 "$debugfile"
       strip --remove-section=.comment --remove-section=.note --strip-unneeded "$1"
       objcopy --add-gnu-debuglink "$debugfile" "$1"' - {} ';'

[00:00:00][0713461b][build:hello.bst                     ] SUCCESS Running strip-commands
[--:--:--][0713461b][build:hello.bst                     ] START   Caching artifact
[00:00:00][0713461b][build:hello.bst                     ] SUCCESS Caching artifact
[00:00:06][0713461b][build:hello.bst                     ] SUCCESS autotools/hello/0713461b-build.1730.log
[00:00:22][][] SUCCESS Build

Pipeline Summary
  Total:       3
  Session:     3
  Fetch Queue: processed 0, skipped 3, failed 0 
  Build Queue: processed 3, skipped 0, failed 0

3.3.2. Run the hello world program

We probably know by now what’s going to happen, but let’s run the program we’ve compiled anyway using bst shell:

user@host:~/autotools$ bst shell hello.bst -- hello

[--:--:--][][] START   Loading elements
[00:00:00][][] SUCCESS Loading elements
[--:--:--][][] START   Resolving elements
[00:00:00][][] SUCCESS Resolving elements
[--:--:--][][] START   Resolving cached state
[00:00:00][][] SUCCESS Resolving cached state
[--:--:--][0713461b][ main:hello.bst                     ] START   Staging dependencies
[00:00:01][0713461b][ main:hello.bst                     ] SUCCESS Staging dependencies
[--:--:--][0713461b][ main:hello.bst                     ] START   Integrating sandbox
[00:00:00][0713461b][ main:hello.bst                     ] SUCCESS Integrating sandbox
[--:--:--][0713461b][ main:hello.bst                     ] STATUS  Running command


Hello World!
This is amhello 1.0.

3.4. Summary

Now we’ve used a builtin build element, and we’ve taken a look into how variables work.

When browsing the build elements in the documentation, we are now equipped with a good idea of what an element is going to do, based on their default YAML configuration and any configurations we have in our project. We can also now observe what variables are in effect for the build of a given element, using bst show.