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>eCos User Guide</TH
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>Chapter 28. Manual Configuration</TD
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>Chapter 28. Manual Configuration</TD
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CLASS="SECT1"
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CLASS="SECT1"
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><A
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><A
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NAME="EDITING-THE-SOURCES">Editing the Sources</H1
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NAME="EDITING-THE-SOURCES">Editing the Sources</H1
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><P
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><P
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>For many users, controlling the packages and
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>For many users, controlling the packages and
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manipulating the available configuration options will be
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manipulating the available configuration options will be
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sufficient to create an embedded operating system that meets
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sufficient to create an embedded operating system that meets
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the application's requirements. However, since <SPAN
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the application's requirements. However, since <SPAN
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CLASS="PRODUCTNAME"
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>eCos</SPAN
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> is
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> is
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shipped entirely in source form, it is possible to go
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shipped entirely in source form, it is possible to go
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further when necessary: you can edit the <SPAN
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further when necessary: you can edit the <SPAN
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CLASS="PRODUCTNAME"
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>eCos</SPAN
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> sources themselves. This requires some
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> sources themselves. This requires some
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understanding of the way the <SPAN
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understanding of the way the <SPAN
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CLASS="PRODUCTNAME"
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>eCos</SPAN
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> build system works.
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> build system works.
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</P
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</P
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><P
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><P
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>The most obvious place to edit the source code is directly
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>The most obvious place to edit the source code is directly
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in the component repository. For example, you could
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in the component repository. For example, you could
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edit the file <TT
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edit the file <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>kernel/<TT
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>kernel/<TT
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CLASS="REPLACEABLE"
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CLASS="REPLACEABLE"
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><I
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><I
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><version></I
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><version></I
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></TT
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></TT
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>/src/sync/mutex.cxx</TT
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>/src/sync/mutex.cxx</TT
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>
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>
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to change the way kernel mutexes work, or possibly just to add some
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to change the way kernel mutexes work, or possibly just to add some
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extra diagnostics or assertions. Once the file has been edited,
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extra diagnostics or assertions. Once the file has been edited,
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it is possible to invoke <B
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it is possible to invoke <B
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CLASS="COMMAND"
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CLASS="COMMAND"
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>make</B
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>make</B
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> at
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> at
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the top level of the build tree and the target library will be rebuilt
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the top level of the build tree and the target library will be rebuilt
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as required. A small optimization is possible: the build tree is
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as required. A small optimization is possible: the build tree is
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largely a mirror of the component repository, so it too will contain
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largely a mirror of the component repository, so it too will contain
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a subdirectory <TT
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a subdirectory <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>kernel/<TT
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>kernel/<TT
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CLASS="REPLACEABLE"
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CLASS="REPLACEABLE"
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><I
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><I
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><version></I
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><version></I
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></TT
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></TT
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></TT
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></TT
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>;
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>;
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if make is invoked in this directory
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if make is invoked in this directory
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then it will only check for changes to the kernel sources, which
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then it will only check for changes to the kernel sources, which
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is a bit more efficient than checking for changes throughout the component
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is a bit more efficient than checking for changes throughout the component
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repository. </P
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repository. </P
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><P
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><P
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>Editing a file in the component repository is fine if this
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>Editing a file in the component repository is fine if this
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tree is used for only one <SPAN
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tree is used for only one <SPAN
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CLASS="PRODUCTNAME"
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>eCos</SPAN
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> configuration. If the repository
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> configuration. If the repository
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is used for several different configurations, however, and especially
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is used for several different configurations, however, and especially
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if it is shared by multiple users, then making what may be experimental
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if it is shared by multiple users, then making what may be experimental
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changes to the master sources would be a bad idea. The build system provides
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changes to the master sources would be a bad idea. The build system provides
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an alternative. It is possible to make a copy of the file in the
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an alternative. It is possible to make a copy of the file in the
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build tree, in other words copy <TT
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build tree, in other words copy <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>mutex.cxx</TT
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>mutex.cxx</TT
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> from
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> from
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the <TT
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the <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>kernel/<TT
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>kernel/<TT
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CLASS="REPLACEABLE"
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CLASS="REPLACEABLE"
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><I
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><I
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><version></I
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><version></I
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></TT
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></TT
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>/src/sync</TT
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>/src/sync</TT
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> directory
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> directory
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in the component repository to <TT
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in the component repository to <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>kernel/<TT
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>kernel/<TT
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CLASS="REPLACEABLE"
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CLASS="REPLACEABLE"
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><I
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><I
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><version></I
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><version></I
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></TT
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></TT
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>/src/sync</TT
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>/src/sync</TT
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> in
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> in
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the build tree, and edit the file in the build tree. When <B
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the build tree, and edit the file in the build tree. When <B
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CLASS="COMMAND"
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CLASS="COMMAND"
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>make</B
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>make</B
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> is
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> is
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invoked it will pick up local copies of any of the sources in preference
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invoked it will pick up local copies of any of the sources in preference
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to the master versions in the component repository. Once you have
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to the master versions in the component repository. Once you have
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finished modifying the <SPAN
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finished modifying the <SPAN
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CLASS="PRODUCTNAME"
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CLASS="PRODUCTNAME"
|
>eCos</SPAN
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>eCos</SPAN
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> sources you can install the final version
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> sources you can install the final version
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back in the component repository. If the changes were temporary
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back in the component repository. If the changes were temporary
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in nature and only served to aid the debugging process, then you
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in nature and only served to aid the debugging process, then you
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can discard the modified version of the sources. </P
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can discard the modified version of the sources. </P
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><P
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><P
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>The situation is slightly more complicated for the header
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>The situation is slightly more complicated for the header
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files that a package may export, such as the C library’s <TT
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files that a package may export, such as the C library’s <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>stdio.h</TT
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>stdio.h</TT
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> header
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> header
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file, which can be found in the directory <TT
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file, which can be found in the directory <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>language/c/libc/<TT
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>language/c/libc/<TT
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CLASS="REPLACEABLE"
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CLASS="REPLACEABLE"
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><I
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><I
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><version></I
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><version></I
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></TT
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></TT
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>/include</TT
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>/include</TT
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>.
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>.
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If such a header file is changed, either directly in the component
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If such a header file is changed, either directly in the component
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repository or after copying it to the build tree, then <B
|
repository or after copying it to the build tree, then <B
|
CLASS="COMMAND"
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CLASS="COMMAND"
|
>make</B
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>make</B
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> must
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> must
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be invoked at the top level of the build tree. In cases like this
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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
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it is not safe to rebuild just the C library because other packages
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may depend on the contents of <TT
|
may depend on the contents of <TT
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CLASS="FILENAME"
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CLASS="FILENAME"
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>stdio.h</TT
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>stdio.h</TT
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>. </P
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>. </P
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>Editing an <SPAN
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>Editing an <SPAN
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>eCos</SPAN
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>eCos</SPAN
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> Savefile</TD
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> Savefile</TD
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>Modifying the Memory Layout</TD
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>Modifying the Memory Layout</TD
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