Disable single warning error

Question

Is there a way to disable just a single warning line in a cpp file with visual studio   For example  if I catch an exception and don t handle it  I get error 4101  unreferenced local variable   Is there a way to ignore this just in that function  but otherwise report it in the compilation unit  At the moment  I put  pragma warning  disable   4101  at the top of the file  but that obviously just turns it off for the whole unit

User · Answer

pragma push pop are often a solution for this kind of problems  but in this case why don t you just remove the unreferenced variable   try                catch const your exception type  amp      type specified but no variable declared

User · Answer

as  rampion mentioned  if you are in clang gcc  the warnings are by name  not number  and you ll need to do    pragma clang diagnostic push  pragma clang diagnostic ignored  -Wunused-variable       your code    pragma clang diagnostic pop   this info comes from here

User · Answer

pragma warning  push    pragma warning  disable   4101     Your function  pragma warning  pop

User · Answer

Example    pragma warning suppress 0000       suppress one error in the next line    This pragma is valid for C   starting with Visual Studio 2005  https   msdn microsoft com en-us library 2c8f766e v vs 80  aspx  The pragma is NOT valid for C  through Visual Studio 2005 through Visual Studio 2015  Error   Expected disable or restore    I guess they never got around to implementing suppress      https   msdn microsoft com en-us library 441722ys v vs 140  aspx  C  needs a different format  It would look like this  but not work     pragma warning suppress 0642      suppress one error in the next line    Instead of suppress  you have to disable and enable   if  condition   pragma warning disable 0642           Empty statement HERE provokes Warning   Possible mistaken empty statement   CS0642   pragma warning restore 0642 else   That is SO ugly  I think it is smarter to just re-style it   if  condition           Do nothing  because blah blah blah     else

User · Answer

Use  pragma warning   push    then  pragma warning   disable    then put your code  then use  pragma warning   pop   as described here    pragma warning  push    pragma warning  disable   WarningCode     code with warning  pragma warning  pop

User · Answer

If you want to disable unreferenced local variable write in some header  template lt class T gt  void ignore  const T  amp         and use   catch const Except  amp  excpt        ignore excpt      No warning

User · Answer

One may also use UNREFERENCED PARAMETER defined in WinNT H  The definition is just    define UNREFERENCED PARAMETER P            P    And use it like   void OnMessage WPARAM wParam  LPARAM lParam        UNREFERENCED PARAMETER wParam       UNREFERENCED PARAMETER lParam       Why would you use it  you might argue that you can just omit the variable name itself  Well  there are cases  different project configuration  Debug Release builds  where the variable might actually be used  In another configuration that variable stands unused  and hence the warning    Some static code analysis may still give warning for this non-nonsensical statement  wParam    In that case  you mayuse DBG UNREFERENCED PARAMETER which is same as UNREFERENCED PARAMETER in debug builds  and does P P in release build     define DBG UNREFERENCED PARAMETER P        P     P

User · Answer

This question comes up as one of the top 3 hits for the Google search for  quot how to suppress -Wunused-result in c   quot   so I m adding this answer here since I figured it out and want to help the next person  In case your warning error is -Wunused  or one of its sub-errors  or -Wunused -Werror only  the solution is to cast to void  For -Wunused or one of its sub-errors only1  you can just cast it to void to disable the warning  This should work for any compiler and any IDE for both C and C    1Note 1  see gcc documentation here  for example  for a list of these warnings  https   gcc gnu org onlinedocs gcc Warning-Options html  then search for the phrase  quot All the above -Wunused options combined quot  and look there for the main -Wunused warning and above it for its sub-warnings  The sub-warnings that -Wunused contains include   -Wunused-but-set-parameter -Wunused-but-set-variable -Wunused-function -Wunused-label -Wunused-local-typedefs -Wunused-parameter -Wno-unused-result -Wunused-variable -Wunused-const-variable -Wunused-const-variable n -Wunused-value -Wunused   contains all of the above -Wunused options combined  Example of casting to void to suppress this warning     some  quot unused quot  variable you want to keep around int some var   7     turn off  -Wunused  compiler warning for this one variable    by casting it to void  void some var       lt       SOLUTION          For C    this also works on functions which return a variable marked with   nodiscard     C   attribute  nodiscard  since C  17  If a function declared nodiscard or a function returning an enumeration or class declared nodiscard by value is called from a discarded-value expression other than a cast to void  the compiler is encouraged to issue a warning   Source  https   en cppreference com w cpp language attributes nodiscard   So  the solution is to cast the function call to void  as this is actually casting the value returned by the function  which is marked with the   nodiscard   attribute  to void  Example     Some class or struct marked with the C      nodiscard    attribute class   nodiscard   MyNodiscardClass    public         fill in class details here private         fill in class details here        Some function which returns a variable previously marked with    with the C      nodiscard    attribute MyNodiscardClass MyFunc         MyNodiscardClass myNodiscardClass      return myNodiscardClass     int main int argc  char  argv             THE COMPILER WILL COMPLAIN ABOUT THIS FUNCTION CALL        IF YOU HAVE  -Wunused  turned on  since you are         discarding a  quot nodiscard quot  return type by calling this        function and not using its returned value      MyFunc            This is ok  however  as casing the returned value to         void  suppresses this  -Wunused  warning       void MyFunc         lt       SOLUTION            Lastly  you can also use the C  17   maybe unused   attribute  https   en cppreference com w cpp language attributes maybe unused

User · Answer

In certain situations you must have a named parameter but you don t use it directly  For example  I ran into it on VS2010  when  e  is used only inside a decltype statement  the compiler complains but you must have the named varible e     All the above non- pragma suggestions all boil down to just adding a single statement     bool f int e           code not using e    return true     e     use without doing anything

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If you only want to suppress a warning in a single line of code  you can use the suppress warning specifier    pragma warning suppress  4101     here goes your single line of code where the warning occurs   For a single line of code  this works the same as writing the following    pragma warning push   pragma warning disable  4101     here goes your code where the warning occurs  pragma warning pop

User · Answer

Instead of putting it on top of the file  or even a header file   just wrap the code in question with  pragma warning  push     pragma warning  disable  and a matching  pragma warning  pop   as shown here   Although there are some other options  including  pramga warning  once

[c++] Disable single warning error

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