[Bug 1264] Bad initialization of FPU null context buffer in cpu_asm.S

rtems-bugs at rtems.org rtems-bugs at rtems.org
Fri Oct 19 13:22:20 UTC 2007


http://www.rtems.org/bugzilla/show_bug.cgi?id=1264


joel.sherrill at oarcorp.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
           Priority|P3                          |P5




------- Comment #1 from joel.sherrill at oarcorp.com  2007-10-19 08:22 -------
The code you are referencing is copying _CPU_Null_fp_context to the FP context
area of the newly created task.  _CPU_Null_fp_context is initialized during
RTEMS initialization with the state of the FPU inherited from the machine
initial state.

There is NO guarantee any data EXCEPT the .bss contents are zero when the RTEMS
application starts.  See 6.7.8 paragraph 10 from this draft of the C99
standard:

See http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf

You would only see this when you use automatic variables that you are not
initializing.  If you want this behavior to change it would be an enhancement
that is beyond the requirements of any language standard I am aware of.


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