Feature request: warn about unused relational operator

[i-make-robots]

Problem
Intend to write A=B;
Accidentally write A != B, A==B, A<=B, etc.

Currently no warning is thrown that the value returned from the operation is never used.
IMHO the nastiest off-by-one error I can make.

Fix
Throw a warning.
Could be suppressed for those special people who like to write A && B; instead of if(A) B;

AFAIK Java IDEs like Eclipse already warn about such behavior. Perhaps this fix could be modeled after that one.

Thank you! I really appreciate all that you do for coders everywhere.

[matthijskooijman]

I think you can enable this one by enabling warnings in the preferences. Would that solve your issue?

It might be good to turn these warnings on by default, but I think there's a bug report about that already.

[per1234]

If you compile the following sketch with File > Preferences > Compiler warnings set to "More" or "All":

void setup() {
  byte A = 1;
  byte B = 2;
  A != B;
  A == B;
  A <= B;
}

void loop() {}

You will get the following warnings:

E:\\arduino\\StatementHasNoEffect\StatementHasNoEffect.ino:4:5: warning: statement has no effect [-Wunused-value]

   A != B;

     ^

E:\\arduino\\StatementHasNoEffect\StatementHasNoEffect.ino:5:5: warning: statement has no effect [-Wunused-value]

   A == B;

     ^

E:\\arduino\\StatementHasNoEffect\StatementHasNoEffect.ino:6:5: warning: statement has no effect [-Wunused-value]

   A <= B;

     ^

Here's the issue for having the warnings on by default: arduino/arduino-ide#1630

[i-make-robots]

Oh, thank you!

…

On Tue, Feb 5, 2019 at 3:12 PM per1234 ***@***.***> wrote: If you compile the following sketch with *File > Preferences > Compiler warnings* set to "More" or "All": void setup() { byte A = 1; byte B = 2; A != B; A == B; A <= B; } void loop() {} You will get the following warnings: E:\\arduino\\StatementHasNoEffect\StatementHasNoEffect.ino:4:5: warning: statement has no effect [-Wunused-value] A != B; ^ E:\\arduino\\StatementHasNoEffect\StatementHasNoEffect.ino:5:5: warning: statement has no effect [-Wunused-value] A == B; ^ E:\\arduino\\StatementHasNoEffect\StatementHasNoEffect.ino:6:5: warning: statement has no effect [-Wunused-value] A <= B; ^ Here's the issue for having the warnings on by default: arduino/arduino-ide#1630 <arduino/arduino-ide#1630> — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#8501 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABZYhnW31sZePn7kdRAEq-ejJs18Tfz6ks5vKg_3gaJpZM4akNIX> .

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