Compilation error using "template <class T>" (prototypes generated incorrectly)

[GoogleCodeExporter]

I found an error using the last revision of Arduino IDE (0022).
This code doesn't compile correctly:

template <class T> int SRAM_writeAnything(int ee, const T& value)
{
    const byte* p = (const byte*)(const void*)&value;
    int i;
    for (i = 0; i < sizeof(value); i++)
      EEPROM.write(ee++, *p++);
    return i;
}

template <class T> int SRAM_readAnything(int ee, T& value)
{
    byte* p = (byte*)(void*)&value;
    int i;
    for (i = 0; i < sizeof(value); i++)
      *p++ = EEPROM.read(ee++);
    return i;
}

The IDE returns this error:
error: expected ',' or '...' before '&' token
error: ISO C++ forbids declaration of 'T' with no type
error: 'T' has not been declared

Using version 0021 it works fine.

Original issue reported on code.google.com by leomi...@gmail.com on 6 Feb 2011 at 3:31

[GoogleCodeExporter]

This is probably caused by the switch from the old oro.jar regular-expressions 
to the standard Java ones: 
<https://github.com/arduino/Arduino/commit/fa4d0582970e50c574ecfdcdbcfeae3754ca2
095>.  Properly generating function prototypes for the full range of C++ syntax 
is tricky, so you might be better off putting the templated function 
definitions in a separate header file in your sketch, which won't be 
pre-processed.  

Patches to the pre-processing code are welcome, too, although need to be well 
tested.

Original comment by dmel...@gmail.com on 21 Feb 2011 at 3:42

• Added labels: Component-IDE

[GoogleCodeExporter]

Might it be helpful to put something in the programming documentation to this 
effect (that is, template functions are best pushed to separate header files 
that don't get pre-processed)?

I looked over the regex for the change, this would've bounced on the Perl5 
regex class in oro.jar, I'm pretty sure. Unless the submitter knows otherwise.

Original comment by WineBizR...@gmail.com on 9 Mar 2011 at 6:48

[GoogleCodeExporter]

This is still active in version 1.0.1 of the IDE. Simple example:

template <typename T> T myAbs (const T a)
  {
  return (a < 0) ? - a : a;
  } // end of myAbs

void setup () {}
void loop () {}

Gives error:

sketch_jun21a:-1: error: 'T' does not name a type

It can't be too hard to fix the regexp to at least handle that, and similar, 
can it? eg.

Optional: template < ... > preceding the function declaration.

Original comment by n...@gammon.com.au on 20 Jun 2012 at 9:06

[GoogleCodeExporter]

Original comment by dmel...@gmail.com on 31 Jul 2012 at 12:48

• Changed title: Compilation error using "template " (prototypes generated incorrectly)
• Added labels: Component-PreProcessor

[GoogleCodeExporter]

New preprocessor tracked at https://github.com/arduino/Arduino/pull/2636. 
Builds for testing it are available

Original comment by federico...@gmail.com on 13 Feb 2015 at 7:18