Conflicting type for first argument of utoa with stdlib.h declaration

[jlbirccyn]

Hello

In hardware/arduino/sam/cores/arduino/itoa.h utoa is declared as follow:

extern char* utoa( unsigned long value, char *string, int radix ) ;

in a gcc 4.9.3 for arm distribution, it conflicts with the declaration of the built-in utoa:

char *  _EXFUN(__utoa,(unsigned, char *, int));

(_EXFUN is defined as follow #define _EXFUN(name, proto) __cdecl name proto )

[cmaglie]

Is this specific for arm-gcc 4.9.3 or for other versions as well?
Can you provide a test sketch?

[jlbirccyn]

Seems to be with 4.9.3. I do not have the error with 4.9.2. No need to provide a sketch. Go in hardware/arduino/sam/cores/arduino and type arm-none-eabi-gcc -c -o test.o -I. WString.cpp (or whatever name your compiler have, provided it is 4.9.3). You can get a 4.9.3 from https://launchpad.net/gcc-arm-embedded

You should get the following error:

In file included from WString.cpp:23:0:
itoa.h:34:65: error: conflicting declaration of C function 'char* utoa(long unsigned int, char*, int)'
 extern char* utoa( unsigned long value, char *string, int radix ) ;
                                                                 ^
In file included from /Users/jlb/Tools/gcc/gcc-arm-none-eabi/arm-none-eabi/include/stdlib.h:11:0,
                 from WString.h:26,
                 from WString.cpp:22:
/Users/jlb/Tools/gcc/gcc-arm-none-eabi/arm-none-eabi/include/stdlib.h:184:8: note: previous declaration 'char* utoa(unsigned int, char*, int)'
 char * _EXFUN(utoa,(unsigned, char *, int));
        ^
WString.cpp: In constructor 'String::String(unsigned char, unsigned char)':
WString.cpp:74:23: error: call of overloaded 'utoa(unsigned char&, char [9], unsigned char&)' is ambiguous
  utoa(value, buf, base);
                       ^
WString.cpp:74:23: note: candidates are:
In file included from /Users/jlb/Tools/gcc/gcc-arm-none-eabi/arm-none-eabi/include/stdlib.h:11:0,
                 from WString.h:26,
                 from WString.cpp:22:
/Users/jlb/Tools/gcc/gcc-arm-none-eabi/arm-none-eabi/include/stdlib.h:184:8: note: char* utoa(unsigned int, char*, int)
 char * _EXFUN(utoa,(unsigned, char *, int));
        ^
In file included from WString.cpp:23:0:
itoa.h:34:14: note: char* utoa(long unsigned int, char*, int)
 extern char* utoa( unsigned long value, char *string, int radix ) ;
              ^

[jsanchezgarcia]

any updates on this?

[neojou]

I have the same problem when trying to upgrade toolchain from 4.8.3 to 5.2.1.

It looks like we can not use utoa(unsigned long value,... ) but utoa(unsigned int value, ... ),
since there is another ultoa() for unsigned long value.

in itoa.c and itoa.h

[patrickelectric]

Same error here 😞

[jlbirccyn]

Just sent a pull request to fix the problem

[cmaglie]

Should be fixed with #5480.

Please reopen, or furhter comment, if not.

[clovisf]

I have tested (and confirm it works) this fix with Arduino IDE Nightly Build 1.6.13 on windows 10 using a third-party board with ATSAMD21G18A, after burning the latest Arduino Zero bootloader to it using ATMEL Studio 7.0