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glibc: Drop --with-headers in pass 1

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I cannot see why this is ever needed.  The default is "the compiler
default" which should be correct as the compiler has been configured
--with-sysroot.  And the explanation for this switch is just repeating a
common misunderstanding.  In fact glibc **never** attempts to figure out
what features the kernel has from the headers.  Instead it depends on
the kernel-features.h files in the source tree and the --with-kernel
value to determine the kernel features that it can rely on.
This commit is contained in:
Xi Ruoyao 2025-03-27 20:56:55 +08:00
parent 5e3bef69d1
commit 7e4fd2e198
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2 changed files with 9 additions and 28 deletions
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11
chapter05/glibc.xml
View File

@ -91,7 +91,6 @@ cd build</userinput></screen>
--host=$LFS_TGT \
--build=$(../scripts/config.guess) \
--enable-kernel=&min-kernel; \
--with-headers=$LFS/usr/include \
--disable-nscd \
libc_cv_slibdir=/usr/lib</userinput></screen>
@ -116,16 +115,6 @@ cd build</userinput></screen>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>--with-headers=$LFS/usr/include</parameter></term>
<listitem>
<para>This tells Glibc to compile itself against the headers
recently installed to the $LFS/usr/include directory, so that
it knows exactly what features the kernel has and can optimize
itself accordingly.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>libc_cv_slibdir=/usr/lib</parameter></term>
<listitem>

26
part3intro/toolchaintechnotes.xml
View File

@ -439,27 +439,19 @@ checking what linker to use... /mnt/lfs/tools/i686-lfs-linux-gnu/bin/ld</compute
standard C library (glibc) to interface with features that the Linux
kernel will provide.</para>
<para>Next comes glibc. The most important
considerations for building glibc are the compiler, binary tools, and
kernel headers. The compiler and binary tools are not an issue
as <parameter>--host=$LFS_TGT</parameter> makes the build system to use
those tools prefixed with <literal>$LFS_TGT-</literal> as we've
discussed. The kernel headers can
be a bit more complicated. Therefore, we take no risks and use
the available configure switch to enforce the correct selection. After
the run of <command>configure</command>, check the contents of the
<filename>config.make</filename> file in the <filename
class="directory">build</filename> directory for all important details.
These items highlight an important aspect of the glibc
package&mdash;it is very self-sufficient in terms of its build machinery,
and generally does not rely on toolchain defaults.</para>
<para>Next comes glibc. This is the first package that we cross-compile.
We use the <parameter>--host=$LFS_TGT</parameter> option to make
the build system to use those tools prefixed with
<literal>$LFS_TGT-</literal>, and the
<parameter>--build=$(../scripts/config.guess)</parameter> option to
enable <quote>the cross-compilation mode</quote> as we've discussed.
The <envar>DESTDIR</envar> variable is used to force installation into
the LFS file system.</para>
<para>As mentioned above, the standard C++ library is compiled next, followed in
<xref linkend="chapter-temporary-tools"/> by other programs that must
be cross-compiled to break circular dependencies at build time.
The install step of all those packages uses the
<envar>DESTDIR</envar> variable to force installation
in the LFS filesystem.</para>
The steps for those packages are similar to the steps for glibc.</para>
<para>At the end of <xref linkend="chapter-temporary-tools"/> the native
LFS compiler is installed. First binutils-pass2 is built,