[FE training-materials-updates] slides/autotools-usage: one slide about cache variables

[Thomas Petazzoni]

Repository : git://git.free-electrons.com/training-materials.git

On branch  : master
Link       : http://git.free-electrons.com/training-materials/commit/?id=21bd2997f312e020ebf9f9b48c901899b6c7b7ba

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commit 21bd2997f312e020ebf9f9b48c901899b6c7b7ba
Author: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Date:   Thu May 21 17:51:46 2015 +0200

    slides/autotools-usage: one slide about cache variables
    
    Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>


>---------------------------------------------------------------

21bd2997f312e020ebf9f9b48c901899b6c7b7ba
 slides/autotools-usage/autotools-usage.tex | 38 ++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/slides/autotools-usage/autotools-usage.tex b/slides/autotools-usage/autotools-usage.tex
index af5e1a5..af41994 100644
--- a/slides/autotools-usage/autotools-usage.tex
+++ b/slides/autotools-usage/autotools-usage.tex
@@ -447,6 +447,44 @@ configure:18210: error:
   \end{itemize}
 \end{frame}
 
+\begin{frame}[fragile]{Cache variables}
+
+  \begin{itemize}
+
+  \item Each test done by a \code{configure.ac} script is associated
+    with a {\em cache variable}
+
+  \item The list of such variables and their values is visible in
+    \code{config.log}:
+    \begin{block}{}
+{\tiny
+\begin{verbatim}
+## ---------------- ##
+## Cache variables. ##
+## ---------------- ##
+ac_cv_build=x86_64-unknown-linux-gnu
+ac_cv_c_compiler_gnu=yes
+[...]
+ac_cv_path_SED=/bin/sed
+\end{verbatim}}
+    \end{block}
+
+  \item If the autodetected value is not correct for some reason, you
+    can override any of these variables in the environment:
+    \begin{block}{}
+{\scriptsize
+\begin{verbatim}
+$ ac_cv_path_SED=/path/to/sed ./configure
+\end{verbatim}}
+    \end{block}
+
+  \item This is sometimes useful when cross-compiling, since some
+    tests are not always cross-compilation friendly.
+
+  \end{itemize}
+
+\end{frame}
+
 \begin{frame}{Distribution}
   \begin{itemize}
   \item In general: