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->Editing the Sources</TITLE
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-TITLE="Manual Configuration"
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-TITLE="Editing an eCos Savefile"
-HREF="editing-an-ecos-savefile.html"><LINK
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-TITLE="Modifying the Memory Layout"
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-><A
-NAME="EDITING-THE-SOURCES">Editing the Sources</H1
-><P
->For many users, controlling the packages and
- manipulating the available configuration options will be
- sufficient to create an embedded operating system that meets
- the application's requirements. However, since <SPAN
-CLASS="PRODUCTNAME"
->eCos</SPAN
-> is
- shipped entirely in source form, it is possible to go
- further when necessary: you can edit the <SPAN
-CLASS="PRODUCTNAME"
->eCos</SPAN
-> sources themselves. This requires some
- understanding of the way the <SPAN
-CLASS="PRODUCTNAME"
->eCos</SPAN
-> build system works.
- </P
-><P
->The most obvious place to edit the source code is directly
-in the component repository. For example, you could
-edit the file <TT
-CLASS="FILENAME"
->kernel/<TT
-CLASS="REPLACEABLE"
-><I
-><version></I
-></TT
->/src/sync/mutex.cxx</TT
->
-to change the way kernel mutexes work, or possibly just to add some
-extra diagnostics or assertions. Once the file has been edited,
-it is possible to invoke <B
-CLASS="COMMAND"
->make</B
-> at
-the top level of the build tree and the target library will be rebuilt
-as required. A small optimization is possible: the build tree is
-largely a mirror of the component repository, so it too will contain
-a subdirectory <TT
-CLASS="FILENAME"
->kernel/<TT
-CLASS="REPLACEABLE"
-><I
-><version></I
-></TT
-></TT
->;
-if make is invoked in this directory
-then it will only check for changes to the kernel sources, which
-is a bit more efficient than checking for changes throughout the component
-repository. </P
-><P
->Editing a file in the component repository is fine if this
-tree is used for only one <SPAN
-CLASS="PRODUCTNAME"
->eCos</SPAN
-> configuration. If the repository
-is used for several different configurations, however, and especially
-if it is shared by multiple users, then making what may be experimental
-changes to the master sources would be a bad idea. The build system provides
-an alternative. It is possible to make a copy of the file in the
-build tree, in other words copy <TT
-CLASS="FILENAME"
->mutex.cxx</TT
-> from
-the <TT
-CLASS="FILENAME"
->kernel/<TT
-CLASS="REPLACEABLE"
-><I
-><version></I
-></TT
->/src/sync</TT
-> directory
-in the component repository to <TT
-CLASS="FILENAME"
->kernel/<TT
-CLASS="REPLACEABLE"
-><I
-><version></I
-></TT
->/src/sync</TT
-> in
-the build tree, and edit the file in the build tree. When <B
-CLASS="COMMAND"
->make</B
-> is
-invoked it will pick up local copies of any of the sources in preference
-to the master versions in the component repository. Once you have
-finished modifying the <SPAN
-CLASS="PRODUCTNAME"
->eCos</SPAN
-> sources you can install the final version
-back in the component repository. If the changes were temporary
-in nature and only served to aid the debugging process, then you
-can discard the modified version of the sources. </P
-><P
->The situation is slightly more complicated for the header
-files that a package may export, such as the C library’s <TT
-CLASS="FILENAME"
->stdio.h</TT
-> header
-file, which can be found in the directory <TT
-CLASS="FILENAME"
->language/c/libc/<TT
-CLASS="REPLACEABLE"
-><I
-><version></I
-></TT
->/include</TT
->.
-If such a header file is changed, either directly in the component
-repository or after copying it to the build tree, then <B
-CLASS="COMMAND"
->make</B
-> must
-be invoked at the top level of the build tree. In cases like this
-it is not safe to rebuild just the C library because other packages
-may depend on the contents of <TT
-CLASS="FILENAME"
->stdio.h</TT
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