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8.15. Flex 2.6.4

Build and install Flex in the final target environment to provide lex-compatible scanner generation.

Input assumption: flex-2.6.4.tar.gz is already present in /sources from the chapter 4 source staging step.

Source URL: https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz

Upstream build note: the release tarball includes a generated configure script, generated parser and scanner sources, and prebuilt manual pages. Upstream documents the normal build flow as configure, make, and make install.

Tool note: Flex requires an m4 implementation that supports -P; chapter 6 installs om4 as the target m4 command.

Licenses:

BSD-style Flex license

Dependencies:

musl (libc)
m4
make

Flex is a fast lexical analyzer generator. we need it to provide final target flex, lex, and libfl support for packages that generate scanners during their build.

Extract and Enter the Source Tree

cd /sources
tar -xf flex-2.6.4.tar.gz
cd flex-2.6.4

Configure Flex

lbi_configure \
    --docdir=/system/documentation/flex \
    --disable-static \
    --enable-shared \
    --disable-nls

Build Flex

make $LWI_MAKE_FLAGS

Install Flex

make install

Install lex Compatibility Links

ln -sf flex /system/binaries/lex
ln -sf flex.1 /system/documentation/man-pages/man1/lex.1

After this step is complete, you can remove the extracted source directory and source tarball from /sources if you do not plan to rebuild Flex again.

Command Explanations

cd /sources, tar -xf, and cd flex-...: Enter the staged Flex source tree.
lbi_configure: Applies the book's /system install layout.
--docdir=/system/documentation/flex: Places package documentation in the documentation tree.
--disable-static and --enable-shared: Build shared libraries without static archives.
--disable-nls: Avoids gettext/native language support.
make $LWI_MAKE_FLAGS and make install: Build and install Flex.
ln -sf flex ... lex and ln -sf flex.1 ... lex.1: Provide traditional lex command and manual-page aliases.

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