Modified Arduino.h with changes to the boolean type

[Chris--A]

As the Arduino specific boolean type is dangerous in C++, I have implemented a fix to solve the situation for both C and C++ There is also no need for stdbool, it also defines true and false, which is not needed or allowed in a C++ context.

This is in reference to the issue I posted here.

#2147

[Chris--A]

I have modified the code to only have the changes. I also replied here #2147 (comment) as to why my idea is worth implementing. For the features stdbool provides, I recommend adding it to only add in C if it must be used, there is no reason to change the current bool, true, or false in C++. And simply to avoid compilation overhead it can be left out altogether, Arduino.h does get included extensively. Also you pointed out that _Bool is an extension for gcc, why not just use the standard implementation (when in C++).

[Chris--A]

Also, if you'd rather keep the stdbool functionality, I can modify my pull request to leave it in.
My main goal here is to get the boolean data type fixed for C++ code. The true/false problem is solved using stdbool or my original code so that is not an issue anymore.

[Chris--A]

This is the important part of my addition. The boolean type needs to be seen as a bool when compiling C++ code.

[ArduinoBot]

Can one of the admins verify this patch?

[xxxajk]

I think that stdbool.h should be used, as it will actually do the right thing.
Next, use a define for boolean and define it as _Bool instead of using a typedef.

[Chris--A]

Stdbool.h doesn't really solve anything though. As you can see its the typedef in Arduino.h which is the problem. bool is just an alias for _Bool in C code. Infact in C++ code it is defined as: #define _Bool bool, which leaves no need for the library, or the time an additional include imposes on the compilation. (Arduino.h with my small changes already implements what stdbool.h does in its entirety ).

[xxxajk]

Yes, but is the type correct? I can't tell from the diff.

[Chris--A]

It effectively adds this:

 #ifdef __cplusplus
    typedef bool boolean;
#else
    typedef uint8_t boolean;
    #define false 0
    #define true !false
#endif

So in C++ boolean is an alias for bool.
And in C boolean is an alias for an unsigned char.
The standard only explicitly gives false a value, so true is its opposite (!false), and in C++ they are actual bool types provided by the standard.

Basically I do not mind how this is implemented, I just insist that the Arduino custom type be a real bool, and true/false not be defines. (in C++). This is a serious bug in my opinion.

• Why boolean needs to be a bool: http://forum.arduino.cc/index.php?topic=252120.msg1785228#msg1785228 See code example in post.
• Why true/false must not be defines in C++ http://forum.arduino.cc/index.php?topic=252120.msg1786908#msg1786908

Also stdbool.h uses a GCC specific _Bool, so if someone changes the platform.txt file to use -c++98/-c++11 instead of -gnu++98/-gnu++11 the Arduino API will not compile.

The third commit doesn't belong here, If this fix is going to be used I will remove it and merge the remaining commits once I can get Arduino cloned on my PC.

[xxxajk]

I wouldn't worry so much with porting. I highly doubt the Arduino team will
use anything other than GNU tools in the foreseeable future.

On Sun, Dec 21, 2014 at 7:33 AM, Christopher Andrews <
notifications@github.com> wrote:

It effectively adds this:

#ifdef __cplusplus
typedef bool boolean;
#else
typedef uint8_t boolean;
#define false 0
#define true !false
#endif

So in C++ boolean is an alias for bool.
And in C boolean is an alias for an unsigned char.
The standard only explicitly gives false a value, so true is its opposite
(!false), and in C++ they are actual bool types provided by the standard.

Basically I do not mind how this is implemented, I just insist that the
Arduino custom type be a real bool, and true/false not be defines. (in
C++). This is a serious bug in my opinion.

• Why boolean needs to be a bool:
  http://forum.arduino.cc/index.php?topic=252120.msg1785228#msg1785228
  See code example in post.
• Why true/false must not be defines in C++
  http://forum.arduino.cc/index.php?topic=252120.msg1786908#msg1786908

Also stdbool.h uses a GCC specific _Bool, so if someone changes the
platform.txt file to use -c++98/-c++11 instead of -gnu++98/-gnu++11 the
Arduino API will not compile.

The third commit doesn't belong here, If this fix is going to be used I
will remove it and merge the remaining commits once I can get Arduino
cloned on my PC.

—
Reply to this email directly or view it on GitHub
#2151 (comment).

Visit my github for awesome Arduino code @ https://github.com/xxxajk

[cmaglie]

From:
http://www.cplusplus.com/reference/cstdbool/
http://www.c-faq.com/bool/booltype.html
http://stackoverflow.com/questions/1608318/is-bool-a-native-c-type

it seems that _Bool is not gcc specific but part of C99

The purpose in C of this header (stdbool.h) is to add a bool type and the true and false values as macro definitions.
In C++, which supports those directly, the header simply contains a macro that can be used to check if the type is supported:

So it's sufficient to include stdbool.h to have a proper bool type defined.
I'd like to leave all the boring definition of true/false etc. to stdbool.h and change only the following:

 #define bit(b) (1UL << (b))

-typedef uint8_t boolean;
+typedef bool boolean;
 typedef uint8_t byte;

 void init(void);

What do you think?

[xxxajk]

That is exactly what I was saying :-)

On Tue, Jan 6, 2015 at 4:43 PM, Cristian Maglie notifications@github.com
wrote:

From:
http://www.cplusplus.com/reference/cstdbool/
http://www.c-faq.com/bool/booltype.html
http://stackoverflow.com/questions/1608318/is-bool-a-native-c-type

it seems that _Bool is not gcc specific but part of C99

The purpose in C of this header (stdbool.h) is to add a bool type and the
true and false values as macro definitions.
In C++, which supports those directly, the header simply contains a macro
that can be used to check if the type is supported:

So it's sufficient to include stdbool.h to have a proper bool type
defined.
I'd like to leave all the boring definition of true/false etc. to
stdbool.h and change only the following:

#define bit(b) (1UL << (b))
-typedef uint8_t boolean;+typedef bool boolean;
typedef uint8_t byte;

void init(void);

What do you think?

—
Reply to this email directly or view it on GitHub
#2151 (comment).

Visit my github for awesome Arduino code @ https://github.com/xxxajk

[matthijskooijman]

+1

[PaulStoffregen]

FWIW, I merged a version for this fix on Teensy, using this:

+// fix C++ boolean issue
+// https://github.com/arduino/Arduino/pull/2151
+#ifdef __cplusplus
+typedef bool boolean;
+#else
+typedef uint8_t boolean;
+#define false 0
+#define true (!false)
+#endif

[Chris--A]

@cmaglie That is excellent. All that is important to me is correct semantics in C++.

Sorry @xxajk, the GCC documentation led me to believe it was an extension/GCC only.

[cmaglie]

Fixed with 20ac20f