On Thu, Jul 25, 2013 at 10:39:09PM -0400, Ian Chapman wrote:
> I'm using - msp430-gcc (GCC) 4.6.3 20120301 (mspgcc LTS 20120406
> unpatched)- and it fails on
>
> extern unsigned short int ContactThreshold;
>
> giving this error
>
> msp430-gcc -Os -Wall -g -mmcu=msp430f5438a main.cpp
> /tmp/cciyW9nS.o: In function `SetSensitivity(unsigned short)':
> /home/stan/msp430/Ovi_Stuff/main.cpp:258: undefined reference to
> `ContactThreshold'
>
> If I junk extern it compiles and once I get there I expect a linker
> error with ContactThreshold defined in two places.
>
> Any suggestions appreciated. Ian. Oh and it did compile with windows.
> Maybe I should change to straight c in place of cpp.
Hi Ian,
The "extern" keyword means that ContactThreshold is defined in another
compilation unit. That is:
unsigned short int ContactTheshold;
...defines a variable called ContactThreshold. If you prefix it with
"extern", you aren't defining it -- you're telling the compiler that it
exists and is defined somewhere else.
Since you appear to be compiling only a single file, "extern" is
probably not what you want.
- Daniel
--
Daniel Beer <[email protected]> www.dlbeer.co.nz
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