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<HTML
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><HEAD
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><TITLE
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>Conflicts and constraints</TITLE
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"><LINK
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REL="HOME"
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TITLE="eCos User Guide"
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HREF="ecos-user-guide.html"><LINK
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REL="UP"
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TITLE="Manual Configuration"
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HREF="manual-configuration.html"><LINK
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REL="PREVIOUS"
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TITLE="Creating the Build Tree"
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HREF="creating-build-tree.html"><LINK
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>eCos User Guide</TH
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>Prev</A
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VALIGN="bottom"
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>Chapter 28. Manual Configuration</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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><H1
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CLASS="SECT1"
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><A
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NAME="CONFLICTS-AND-CONSTRAINTS">Conflicts and constraints</H1
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><P
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>Configuration options are not completely independent. For example
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the C library's <TT
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CLASS="FUNCTION"
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>strtod()</TT
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> and <TT
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CLASS="FUNCTION"
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>atof()</TT
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>
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functions rely on the math library package to provide certain functionality. If the math library package is removed then the C
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library can no longer provide these functions. Each package describes constraints like these in CDL <SPAN
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CLASS="emphasis"
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><I
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CLASS="EMPHASIS"
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>"requires"</I
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></SPAN
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> properties. If a constraint is not satisfied, then the configuration contains a conflict. For any given conflict there can
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be several resolution options. For example, it would be possible to add the math library package back to the
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configuration, or to disable the <TT
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CLASS="FUNCTION"
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>strtod()</TT
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> and <TT
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CLASS="FUNCTION"
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>atof()</TT
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> functions.</P
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><P
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>The <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> configuration tools will report any conflicts in the current configuration. If there are any such conflicts
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then the configuration is usually unsafe and it makes no sense to build and run <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> in such circumstances. In fact,
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any attempt at building <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> is likely to fail. In exceptional cases it is possible to override this by using e.g. the
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<TT
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CLASS="OPTION"
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>--ignore-errors</TT
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> qualifier with ecosconfig. </P
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><P
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>Many constraints are fairly simple in nature, and the configuration tools contain an inference engine which can
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resolve the associated conflicts automatically. For example, if the math library package is removed then the
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inference engine can resolve the resulting conflict by disabling the configuration option for <TT
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CLASS="FUNCTION"
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>strtod()</TT
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> and <TT
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CLASS="FUNCTION"
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>atof()</TT
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>. All
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such changes will be reported. Sometimes the inference engine cannot resolve a conflict, for example it is not
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allowed to override a change that has been made explicitly by the user. Sometimes it will find a solution which does
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not match the application's requirements. </P
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><P
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>A typical session involving conflicts would look something like this:
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<TABLE
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BORDER="5"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>$ ecosconfig new pid</PRE
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></TD
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></TR
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></TABLE
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>This creates a new configuration with the default template. For most targets this will not result in any conflicts,
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because the default settings for the various options meet the requirements of the default template.</P
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><P
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> For some targets
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there may be conflicts and the inference engine would come into play.
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<TABLE
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><PRE
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CLASS="SCREEN"
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>$ ecosconfig remove libm
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U CYGSEM_LIBC_STDIO_SCANF_FLOATING_POINT, new inferred value 0
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U CYGFUN_LIBC_strtod, new inferred value 0
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U CYGSEM_LIBC_STDIO_PRINTF_FLOATING_POINT, new inferred value 0 </PRE
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></TD
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></TABLE
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>
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ecosconfig reports that this change caused three conflicts, all in the C library. The inference engine was able to
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resolve all the conflicts and update the relevant configuration options accordingly. </P
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><P
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>To suppress the inference engine <TT
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CLASS="OPTION"
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>--no-resolve</TT
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> can be used:
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<TABLE
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BORDER="5"
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><PRE
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CLASS="SCREEN"
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>$ ecosconfig new pid
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$ ecosconfig --no-resolve remove libm
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C CYGSEM_LIBC_STDIO_SCANF_FLOATING_POINT, "requires" constraint not satisfied: CYGPKG_LIBM
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C CYGSEM_LIBC_STDIO_PRINTF_FLOATING_POINT, "requires" constraint not satisfied: CYGPKG_LIBM
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C CYGFUN_LIBC_strtod, "requires" constraint not satisfied: CYGPKG_LIBM </PRE
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></TD
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></TR
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></TABLE
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>
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Three unresolved conflicts are reported.</P
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><P
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>The <B
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CLASS="COMMAND"
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>check</B
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> command can be used to get the current state of the
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configuration, and the <TT
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CLASS="OPTION"
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>--verbose</TT
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> qualifier will provide additional information: </P
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><TABLE
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BORDER="5"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>$ ecosconfig --srcdir /home/bartv/ecc/ecc --verbose check
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Target: pid
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Template: default
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Removed:
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CYGPKG_LIBM
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3 conflict(s):
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C CYGFUN_LIBC_strtod, "requires" constraint not satisfied: CYGPKG_LIBM
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Possible solution:
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CYGFUN_LIBC_strtod -> 0
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CYGSEM_LIBC_STDIO_SCANF_FLOATING_POINT -> 0
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C CYGSEM_LIBC_STDIO_PRINTF_FLOATING_POINT, "requires" constraint not satisfied: CYGPKG_LIBM
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Possible solution:
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CYGSEM_LIBC_STDIO_PRINTF_FLOATING_POINT -> 0
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C CYGSEM_LIBC_STDIO_SCANF_FLOATING_POINT, "requires" constraint not satisfied: CYGPKG_LIBM
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Possible solution:
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CYGSEM_LIBC_STDIO_SCANF_FLOATING_POINT -> 0 </PRE
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></TD
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></TR
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></TABLE
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><P
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>If the proposed solutions are acceptable, the resolve command can be used to apply them:
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<TABLE
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BORDER="5"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>$ ecosconfig resolve
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U CYGSEM_LIBC_STDIO_SCANF_FLOATING_POINT, new inferred value 0
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U CYGFUN_LIBC_strtod, new inferred value 0
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U CYGSEM_LIBC_STDIO_PRINTF_FLOATING_POINT, new inferred value 0 </PRE
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></TD
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></TR
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></TABLE
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></P
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><P
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>The current configuration is again conflict-free and it is possible to generate a build tree. The <TT
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CLASS="OPTION"
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>--quiet</TT
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> qualifier can
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be used to suppress the change messages, if desired.</P
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><P
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>When changing individual configuration options by editing the ecos.ecc file (as described below), the resulting
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system should be checked and any problems should be resolved. For example, if CYGFUN_LIBC_strtod is
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explicitly enabled in the savefile:
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<TABLE
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BORDER="5"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>$ edit ecos.ecc
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$ ecosconfig check
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Target: pid
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Template: default
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Removed:
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CYGPKG_LIBM
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1 conflict(s):
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C CYGFUN_LIBC_strtod, "requires" constraint not satisfied: CYGPKG_LIBM
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$ ecosconfig resolve
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C CYGFUN_LIBC_strtod, "requires" constraint not satisfied: CYGPKG_LIBM </PRE
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></TD
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></TR
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></TABLE
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>
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In this case the inference engine cannot resolve the conflict automatically because that would involve changing a
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user setting. Any attempt to generate a build tree will fail:
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<TABLE
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BORDER="5"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>$ ecosconfig --srcdir /home/bartv/ecc/ecc tree
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C CYGFUN_LIBC_strtod, "requires" constraint not satisfied: CYGPKG_LIBM
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Unable to generate build tree, this configuration still contains conflicts.
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Either resolve the conflicts or use --ignore-errors </PRE
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></TD
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></TR
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></TABLE
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></P
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><P
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>It is still possible to generate a build tree:
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<TABLE
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BORDER="5"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>$ ecosconfig --srcdir /home/bartv/ecc/ecc --ignore-errors tree
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C CYGFUN_LIBC_strtod, "requires" constraint not satisfied: CYGPKG_LIBM
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$ make </PRE
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></TD
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></TABLE
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>
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In this case <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> will fail to build. In other cases of unresolved conflicts <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
|
| 328 |
|
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> may build, but may not run. In
|
| 329 |
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general all conflicts should be resolved by editing the <TT
|
| 330 |
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CLASS="FILENAME"
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| 331 |
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>ecos.ecc</TT
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| 332 |
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> file, by letting the inference engine make appropriate
|
| 333 |
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changes, or by other means, before any attempt is made to build or run <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>. </P
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></DIV
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><DIV
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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CELLSPACING="0"
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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HREF="creating-build-tree.html"
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>Prev</A
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="ecos-user-guide.html"
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ACCESSKEY="H"
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>Home</A
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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HREF="building-the-system.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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><TR
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>Creating the Build Tree</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="manual-configuration.html"
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ACCESSKEY="U"
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| 390 |
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>Up</A
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| 391 |
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></TD
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><TD
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WIDTH="33%"
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| 394 |
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ALIGN="right"
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VALIGN="top"
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| 396 |
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>Building the System</TD
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></TR
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></TABLE
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