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 Posted: Jul 28, 2012 - 09:37 AM |
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Joined: Oct 10, 2011
Posts: 237
Location: Sydney, Australia
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As a learning experience I have been converting some parts of existing C code to CPP for an atmega16.
I started with AS5.1 and had the application working. I have now moved to AS6 and have a set of issues with the same code:-(
One of the problems is some confusion with methoid signatures.
The first method below calls a putstr routine where the string is in flash; the second where it is in ram.
Code:
void debugQ::putstr( const char *str)
{
putstr_debug_P(str);
}
void debugQ::putstr( char *str)
{
putstr_debug(str);
}
in AS51. this worked well.... the "const" qualifier differentiated between the two methods. in AS6 the first method is always called. as you can imagine this does not work well when the string is in ram....
has anyone had a similar experience?
Are there any suggestions?
Thanks. |
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regards
Greg
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Posted: Jul 28, 2012 - 11:09 AM |
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Joined: Mar 09, 2012
Posts: 1452
Location: North Carolina, USA
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| That's lousy design anyway - neither of them modifies str, so they should both take const parameters. |
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Sid
Life... is a state of mind
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Posted: Jul 28, 2012 - 11:17 AM |
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Joined: Oct 10, 2011
Posts: 237
Location: Sydney, Australia
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| That was not a helpful response. |
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regards
Greg
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Posted: Jul 28, 2012 - 04:12 PM |
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Joined: Mar 27, 2002
Posts: 18520
Location: Lund, Sweden
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This seems to be a bug. AFAIK (gotta read up on it in the standard, or perhaps Stroustrup to be sure...) the "cv-qualifiers" are part of a member function signature.
Advice: Build using both AS51 and AS6. Take steps to get as much build output detail as possible. Study the differences in the two builds to see if there is some option/switch etc that differs. Dig from there..
Also, looking in the GCC bug tracker might reveal something.
You might get more help from the compiler gurus here if you report what versions of the tool chain behaves correctly or incorrectly.
Apart from that, and helpful or not, I tend to agree with Mr Gardiner on the design issue..  |
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Posted: Jul 28, 2012 - 04:22 PM |
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Joined: Jul 23, 2001
Posts: 2437
Location: Osnabrueck, Germany
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Quote:
in AS6 the first method is always called. as you can imagine this does not work well when the string is in ram....
Exactly how have you tested it? "in ram" does not necessarily mean "not const".
E.g. with
Code:
putstr("Hello world!");
of course the first method is called, because a string literal is a "const char *".
Quote:
Apart from that, and helpful or not, I tend to agree with Mr Gardiner on the design issue..
+1 |
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Stefan Ernst
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Posted: Jul 28, 2012 - 04:28 PM |
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Joined: Jul 18, 2005
Posts: 62220
Location: (using avr-gcc in) Finchingfield, Essex, England
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| Presumably you can always cast the parameter to reach the implementation you want? |
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Posted: Jul 28, 2012 - 07:04 PM |
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Joined: Oct 29, 2006
Posts: 2640
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gregd99 wrote:
As a learning experience I have been converting some parts of existing C code to CPP for an atmega16.
I started with AS5.1 and had the application working. I have now moved to AS6 and have a set of issues with the same code:-(
My suspicion is that the AS5.1 C++ compiler did it wrong and the AS6 C++ compiler is doing it right.
Quote:
One of the problems is some confusion with methoid signatures.
The first method below calls a putstr routine where the string is in flash; the second where it is in ram.
Code:
void debugQ::putstr( const char *str)
{
putstr_debug_P(str);
}
void debugQ::putstr( char *str)
{
putstr_debug(str);
}
in AS51. this worked well.... the "const" qualifier differentiated between the two methods. in AS6 the first method is always called. as you can imagine this does not work well when the string is in ram....
The type of "literal" is const char[8], which converts to const char * .
Traditionally, _P has been used to mark functions that use program memory. |
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Michael Hennebry
Iluvatar is the better part of Valar.
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Posted: Jul 28, 2012 - 07:09 PM |
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Joined: Mar 27, 2002
Posts: 18520
Location: Lund, Sweden
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Since three wise men posted after me, I actually re-read your code. My previous response was made in flimsy haste, it seems.
Yes, there is very little to be said about right/wrong, RAM/flash, good/bad and so on without you showing code that calls those functions.
One of my mantras here is: Post a minimal but complete test program that compiles, runs and displays the problem. |
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