leaflabsandy
Member
PC System: Windows XP SP3
Maple Version: 0.5
Problem: goto instruction does not compile.
Note: "no color" on goto
------
Code <---- This compiles
------
void setup() {
}
void loop() {
label1:
goto label1;
}
------
Code <---- This doesn't compile
------
void setup() {
}
void loop() {
goto label1;
label1:
}
poslathian
LeafLabs
hmm. interesting. Does that work in arduino? I havent had the occasion to use goto, but Im not particularly surprised that you cant reference labels before they are declared. We will add this to the docs, thanks for the tip!
p.s. this is an issue of how arm-gcc functions, so I think were just going to have to live with it (but documented!)
leaflabsandy
Member
It works, in the Arduino, if you "add" another instruction after the label: <------
Arduino Example
for(byte r = 0; r < 255; r++){
for(byte g = 255; g > -1; g--){
for(byte b = 0; b < 255; b++){
if (analogRead(0) > 250){ goto bailout;}
// more statements ...
}
}
}
bailout: // <------------- You need to add another instruction after this for it to
// compile !!!!! The example left the next instruction out.BTW ... just killing time checking all the Maple's instruction commands until I get my
USBprint and have the capability to run on external power on my win xp 32 ... Hint Hint
EDITED by bnewbold: put code in code block for readability
perry
Administrator
This is a result of the compiler optimizing away the label.
The code is straight line code, there's nothing between the goto and the label, and there are no instructions at the label, so there's no reason to do the goto (there's nothing to go to!). The compiler is smart enough to recognize this and will simply remove it.
For future reference, we compile with gcc optimization level -Os
Hey andy, thanks for unit testing for us! I quickly ran through all the "bundled" examples to try and catch errors, but we really need to have a full gigantic arduino language unit test sketch that we'll toss in the Maple example directory (and push back to the Arduino team?).
By "no color" on goto did you mean that the 'goto' keyword it turn orange in the IDE? I'm adding SerialUSB and a couple other missing keywords... I might leave 'goto' out to indicate that it isn't really pastel-happy-easy-coding-approved (the same way that a lot of low-level register macros like TIMER3_BASE also get left out). Do you agree?
leaflabsandy
Member
Its your call ... the goto should be in color just like the
other keywords and most users, like me, use this command
to break out from a nested loop so having it in color will
make this command stand out. The goto "label:" keyword changes to a bold light grey.
Note: The Arduino leaves it in black. Doesn't mean it is right?
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