[avr-libc-dev] [bug #36933] Documentation no longer correctly describes how to declare strings for storage in program memory

[Stuart Cording]

URL:
  <http://savannah.nongnu.org/bugs/?36933>

                 Summary: Documentation no longer correctly describes how to
declare strings for storage in program memory
                 Project: AVR C Runtime Library
            Submitted by: codinghead
            Submitted on: Tue 24 Jul 2012 09:44:17 GMT
                Category: Documentation
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Documentation
                  Status: None
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 1.8.0
           Fixed Release: None

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Details:

The documentation page as described below no longer correctly describes how to
define strings that are to be stored in program memory using the PGM_P and
PROGMEM definition s.

This issue occurs when moving from version 1.7.1 to 1.8.0.

Description of the issue with the 1.8.0 library and how to solve it below.

> The strings were defined as per the AVR Libc homepage - 
> http://www.nongnu.org/avr-libc/user-manual/pgmspace.html
>
> They suggest:
> char string_1[] PROGMEM = "String 1";
> char string_2[] PROGMEM = "String 2";
> char string_3[] PROGMEM = "String 3";
> char string_4[] PROGMEM = "String 4";
> char string_5[] PROGMEM = "String 5";
>
> PGM_P string_table[] PROGMEM =
> {
>     string_1,
>     string_2,
>     string_3,
>     string_4,
>     string_5
> };
>
> However, on compiling my code I received the following error for each such
defined line of code:
>
> Error 1       variable 'string_B01' must be const in order to be put into
read-only section by means of '__attribute__((progmem))'
>
> Changing the code to the following resolves the issue:
>
> const char string_1[] PROGMEM = "String 1"; const char string_2[] 
> PROGMEM = "String 2"; const char string_3[] PROGMEM = "String 3"; 
> const char string_4[] PROGMEM = "String 4"; const char string_5[] 
> PROGMEM = "String 5";
>
> PGM_P const string_table[] PROGMEM =
> {
>     string_1,
>     string_2,
>     string_3,
>     string_4,
>     string_5
> };





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