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| -rw-r--r-- | doc/manual/writing-nix-expressions.xml | 251 |
1 files changed, 250 insertions, 1 deletions
diff --git a/doc/manual/writing-nix-expressions.xml b/doc/manual/writing-nix-expressions.xml index 546c0efb3d3d..d1ded020eb71 100644 --- a/doc/manual/writing-nix-expressions.xml +++ b/doc/manual/writing-nix-expressions.xml @@ -1285,7 +1285,256 @@ character, or inline/multi-line, enclosed within <literal>/* <sect1 id='sec-standard-environment'><title>The standard environment</title> -<para>TODO</para> +<para>The standard build environment in the Nix Packages collection +provides a basic environment for building Unix packages. It consists +of the following components: + +<itemizedlist> + + <listitem><para>The GNU C Compiler, configured with C and C++ + support. On Linux, the compiler has been patched to provide greater + <quote>purity</quote> assurance. For instance, the compiler doesn't + search in locations such as <filename>/usr/include</filename>. In + fact, attempts to add such directories through the + <option>-I</option> flag are filtered out. Likewise, the linker + (from GNU binutils) doesn't search in standard locations such as + <filename>/usr/lib</filename>. Programs built on Linux are linked + against a GNU C Library that likewise doesn't search in the default + system locations.</para></listitem> + + <listitem><para>GNU coreutils (contains a few dozen standard Unix + commands).</para></listitem> + + <listitem><para>GNU findutils (contains + <command>find</command>).</para></listitem> + + <listitem><para>GNU diffutils (contains <command>diff</command>, + <command>cmp</command>).</para></listitem> + + <listitem><para>GNU <command>sed</command>.</para></listitem> + + <listitem><para>GNU <command>grep</command>.</para></listitem> + + <listitem><para>GNU <command>awk</command>.</para></listitem> + + <listitem><para>GNU <command>tar</command>.</para></listitem> + + <listitem><para><command>gzip</command> and + <command>bzip2</command>.</para></listitem> + + <listitem><para>GNU Make. It has been patched to provide + <quote>nested</quote> output that can be fed into the + <command>log2xml</command> command and <command>log2html</command> + stylesheet to create a structured, readable output of the build + steps performed by Make.</para></listitem> + + <listitem><para>Bash. This is the shell used for all builders in + the Nix Packages collection. Not using <command>/bin/sh</command> + removes a large source of portability problems.</para></listitem> + + <listitem><para>Patch.</para></listitem> + +</itemizedlist> + +</para> + +<para>The standard environment is used by passing it as an input +called <envar>stdenv</envar> to the derivation, and then doing + +<programlisting> +. $stdenv/setup</programlisting> + +at the top of the builder.</para> + +<para>Apart from adding the aforementioned commands to the +<envar>PATH</envar>, <filename>setup</filename> also does the +following: + +<itemizedlist> + + <listitem><para>All input components specified in the + <envar>buildInputs</envar> environment variable have their + <filename>/bin</filename> subdirectory added to <envar>PATH</envar>, + their <filename>/include</filename> subdirectory added to the C/C++ + header file search path, and their <filename>/lib</filename> + subdirectory added to the linker search path. This can be extended. + For instance, when the <command>pkgconfig</command> component is + used, the subdirectory <filename>/lib/pkgconfig</filename> of each + input is added to the <envar>PKG_CONFIG_PATH</envar> environment + variable.</para></listitem> + + <listitem><para>The environment variable + <envar>NIX_CFLAGS_STRIP</envar> is set so that the compiler strips + debug information from object files. This can be disabled by + setting <envar>NIX_STRIP_DEBUG</envar> to + <literal>0</literal>.</para></listitem> + +</itemizedlist> + +</para> + +<para>The <filename>setup</filename> script also exports a function +called <function>genericBuilder</function> that knows how to build +typical Autoconf-style components. It can be customised to perform +builds for any type of component. It is advisable to use +<function>genericBuild</function> since it provides facilities that +are almost always useful such as unpacking of sources, patching of +sources, nested logging, etc.</para> + +<para>The operation of the generic builder can be modified in many +places by setting certain variables. These <emphasis>hook +variables</emphasis> are typically set to the name of some shell +function defined by you. For instance, to perform some additional +steps after <command>make install</command> you would set the +<varname>postInstall</varname> variable: + +<programlisting> +postInstall=myPostInstall + +myPostInstall() { + mkdir $out/share/extra + cp extrafiles/* $out/share/extra +}</programlisting> + +</para> + +<para>The generic builder has a number of <emphasis>phases</emphasis>, +each of which can be override in its entirety by setting the indicated +variable. The phases are: + +<itemizedlist> + + <listitem> + + <para><function>unpackPhase</function>: unpacks the source files + listed in the <envar>src</envar> environment variable to the + current directory. It supports <filename>tar</filename> files, + optionally compressed with <command>gzip</command> or + <command>bzip2</command>; Zip files (but note that the + <command>unzip</command> command is not a part of the standard + environment; you should add it as a build input yourself); and + unpacked source trees (i.e., directories; they are copied + verbatim). You can add support for other file types by setting + the <varname>findUnpacker</varname> hook. This hook should set an + the variable <varname>unpackCmd</varname> to contain the command + to be executed to unpack the file.</para> + + <para>After unpacking all source files, + <function>unpackPhase</function> changes the current directory to + the directory created by unpacking the sources. If there are + multiple source directories, you should set + <varname>sourceRoot</varname> to the name of the intended + directory.</para> + + <para>It also calls the hook <varname>postUnpack</varname> after + unpacking.</para> + + </listitem> + + <listitem><para><function>patchPhase</function> calls the + <command>patch</command> command with the <option>-p1</option> + option for each patch file listed in the <envar>patches</envar> + variable.</para></listitem> + + <listitem> + + <para><function>configurePhase</function> runs the script called + <filename>configure</filename> in the current directory with a + <option>--prefix</option> set to the output path. You can add + additional flag through the <varname>configureFlags</varname> + variable. If <filename>configure</filename> does not exist, + nothing happens.</para> + + <para>Before and after running <filename>configure</filename>, the + hooks <varname>preConfigure</varname> and + <varname>postConfigure</varname> are called, respectively.</para> + + </listitem> + + <listitem> + + <para><function>buildPhase</function> calls + <command>make</command>. You can set flags for + <command>make</command> through the <varname>makeFlags</varname> + variable.</para> + + <para>Before and after running <command>make</command>, the hooks + <varname>preBuild</varname> and <varname>postBuild</varname> are + called, respectively.</para> + + </listitem> + + <listitem><para><function>checkPhase</function> calls <command>make + check</command>, but only if the <varname>doCheck</varname> variable + is set to <literal>1</literal>. Additional flags can be set through + the <varname>checkFlags</varname> variable.</para></listitem> + + <listitem> + + <para><function>installPhase</function> calls <command>make + install</command>. Additional flags can be set through the + <varname>installFlags</varname> variable. It also strips any + static libraries in the output path of debug information unless + <varname>dontStrip</varname> is set to + <literal>1</literal>.</para> + + <para>Before and after running <command>make install</command>, + the hooks <varname>preInstall</varname> and + <varname>postInstall</varname> are called, respectively.</para> + + </listitem> + + <listitem> + + <para><function>distPhase</function> calls <command>make + dist</command>, but only if the <varname>doDist</varname> variable + is set to <literal>1</literal>. Additional flags can be set + through the <varname>distFlags</varname> variable. The resulting + tarball is copied to the <filename>/tarballs</filename> + subdirectory of the output path.</para> + + <para>Before and after running <command>make dist</command>, the + hooks <varname>preDist</varname> and <varname>postDist</varname> + are called, respectively.</para> + + </listitem> + +</itemizedlist> + +</para> + +<para>You can change the order in which phases are executed, or add +new phases, by setting the <varname>phases</varname> variable. The +default is <literal>patchPhase configurePhase buildPhase checkPhase +installPhase distPhase</literal>.</para> + +<para>At the beginning of each phase, the set of all shell variables +is written to the file <filename>env-vars</filename> at the top-level +build directory. This is useful for debugging: it allows you to +recreate the environment in which a build was performed. For +instance, if a build fails, then assuming you used the +<option>-K</option> flag, you can go to the output directory and +<quote>switch</quote> to the environment of the builder: + +<screen> +$ nix-build -K ./foo.nix +... fails, keeping build directory `/tmp/nix-1234-0' + +$ cd /tmp/nix-1234-0 + +$ source env-vars + +<lineannotation>(edit some files...)</lineannotation> + +$ make + +<lineannotation>(execution continues with the same GCC, make, etc.)</lineannotation></screen> + +</para> + +<para>The definitive, up-to-date documentation of the generic builder +is the source itself, which resides in +<filename>pkgs/stdenv/generic/setup.sh</filename>.</para> </sect1> |