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.

Note

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
aliases:
  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

variables:

  # 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

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

depends:
- 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

3.2.3.1. 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

[--:--:--][][] 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
sysconfdir: /etc
debugdir: /usr/lib/debug
build-root: /buildstream/autotools/hello.bst
make: make
sharedstatedir: /usr/com
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"
prefix: /usr
exec_prefix: /usr
libdir: /usr/lib
objcopy-extract-args: --only-keep-debug --compress-debug-sections
bindir: /usr/bin
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\
  \   "
command-subdir: doc/amhello
sbindir: /usr/sbin
make-install: make -j1 DESTDIR="/buildstream-install" install
libexecdir: /usr/libexec
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\
  \   "
objcopy-link-args: --add-gnu-debuglink
element-name: hello.bst
conf-local:
datadir: /usr/share
project-name: autotools
install-root: /buildstream-install
max-jobs: 2
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\"' - {} ';'"
fix-pyc-timestamps: "find \"/buildstream-install\" -name '*.pyc' -exec \\\n  dd if=/dev/zero\
  \ of={} bs=1 count=4 seek=4 conv=notrunc ';'"
docdir: /usr/share/doc
conf-extra:
includedir: /usr/include
localstatedir: /var
infodir: /usr/share/info
strip-args: --remove-section=.comment --remove-section=.note --strip-unneeded
__bst_provenance_info: /home/user/buildstream/buildstream/data/projectconfig.yaml
  [line 20 column 2]
mandir: /usr/share/man
conf-global:
lib: lib
conf-cmd: ./configure

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

variables:
  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

[--:--:--][][] 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 1.6.9
  Session Start: Tuesday, 21-02-2023 at 14:38:07
  Project:       autotools (/home/user/buildstream/doc/examples/autotools)
  Targets:       hello.bst
  Cache Usage:   12K / infinity (0%)

User Configuration
  Configuration File:      /home/user/buildstream/doc/run-bst-c4z67wh_/buildstream.conf
  Log Files:               /home/user/buildstream/doc/run-bst-c4z67wh_/logs
  Source Mirrors:          /home/user/buildstream/doc/run-bst-c4z67wh_/sources
  Build Area:              /home/user/buildstream/doc/run-bst-c4z67wh_/build
  Artifact Cache:          /home/user/buildstream/doc/run-bst-c4z67wh_/artifacts
  Strict Build Plan:       Yes
  Maximum Fetch Tasks:     10
  Maximum Build Tasks:     4
  Maximum Push Tasks:      4
  Maximum Network Retries: 2

Pipeline
   buildable d5472eb60ceb8a45b0ed5907912b5d89ce91d8a4e9b454ea2663f052c6cf4dff base/alpine.bst 
     waiting 50110d08831106135148d991c33f15794b530938712216e84593eeff7c1ef8ca base.bst 
     waiting 3e973b0426351cd9948d72276133798f231564928935a941990d3bea8b1d3321 hello.bst 
===============================================================================
[--:--:--][d5472eb6][build:base/alpine.bst               ] START   autotools/base-alpine/d5472eb6-build.255.log
[--:--:--][d5472eb6][build:base/alpine.bst               ] START   Staging sources
[00:00:05][d5472eb6][build:base/alpine.bst               ] SUCCESS Staging sources
[--:--:--][d5472eb6][build:base/alpine.bst               ] START   Caching artifact
[00:00:02][d5472eb6][build:base/alpine.bst               ] SUCCESS Caching artifact
[00:00:09][d5472eb6][build:base/alpine.bst               ] SUCCESS autotools/base-alpine/d5472eb6-build.255.log
[--:--:--][50110d08][build:base.bst                      ] START   autotools/base/50110d08-build.257.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.257.log
[--:--:--][3e973b04][build:hello.bst                     ] START   autotools/hello/3e973b04-build.259.log
[--:--:--][3e973b04][build:hello.bst                     ] START   Staging dependencies
[00:00:00][3e973b04][build:hello.bst                     ] SUCCESS Staging dependencies
[--:--:--][3e973b04][build:hello.bst                     ] START   Integrating sandbox
[00:00:00][3e973b04][build:hello.bst                     ] SUCCESS Integrating sandbox
[--:--:--][3e973b04][build:hello.bst                     ] START   Staging sources
[00:00:00][3e973b04][build:hello.bst                     ] SUCCESS Staging sources
[--:--:--][3e973b04][build:hello.bst                     ] START   Running configure-commands
[--:--:--][3e973b04][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;
    fi

[--:--:--][3e973b04][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 \
    --infodir=/usr/share/info   

[00:00:03][3e973b04][build:hello.bst                     ] SUCCESS Running configure-commands
[--:--:--][3e973b04][build:hello.bst                     ] START   Running build-commands
[--:--:--][3e973b04][build:hello.bst                     ] STATUS  Running build-commands

    make

[00:00:00][3e973b04][build:hello.bst                     ] SUCCESS Running build-commands
[--:--:--][3e973b04][build:hello.bst                     ] START   Running install-commands
[--:--:--][3e973b04][build:hello.bst                     ] STATUS  Running install-commands

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

[00:00:00][3e973b04][build:hello.bst                     ] SUCCESS Running install-commands
[--:--:--][3e973b04][build:hello.bst                     ] START   Running strip-commands
[--:--:--][3e973b04][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
       fi
       debugfile="/buildstream-install/usr/lib/debug/$1"
       mkdir -p "$(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][3e973b04][build:hello.bst                     ] SUCCESS Running strip-commands
[--:--:--][3e973b04][build:hello.bst                     ] START   Caching artifact
[00:00:00][3e973b04][build:hello.bst                     ] SUCCESS Caching artifact
[00:00:05][3e973b04][build:hello.bst                     ] SUCCESS autotools/hello/3e973b04-build.259.log
[00:00:14][][] 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
[--:--:--][3e973b04][ main:hello.bst                     ] START   Staging dependencies
[00:00:00][3e973b04][ main:hello.bst                     ] SUCCESS Staging dependencies
[--:--:--][3e973b04][ main:hello.bst                     ] START   Integrating sandbox
[00:00:00][3e973b04][ main:hello.bst                     ] SUCCESS Integrating sandbox
[--:--:--][3e973b04][ main:hello.bst                     ] STATUS  Running command

    hello

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.