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TMS320F28335 compiler v6.2.9: argument of type "const S8 *" is incompatible with parameter of type "const char *"

stevenh
Guru 19935 points

Hello,

My code typedefs unsigned int as a signed char, i.e.

typedef   signed char S8;

Why does the compiler (v6.2.9) produce an "argument of type "const S8 *" is incompatible with parameter of type "const char *" for the code snippet shown below?

strncpy((s8Name, (const S8 *) s8Data, 10);

According to page 92 of the compiler user's guide (spru514g), a signed char and a char should be equivalent data types.

Stephen

 










								


				
				

				
			

		

			
						
									
                			    			                        
						
						
			
			
						
			                        
			
			
				
			  
			

			     
			

		


				    			

						
















	

	

					
    
	
    





		
	
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                          TI__Guru*
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    Are you compiling in C++ mode?  Are you using strict ANSI mode?
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                 	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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						in reply to Archaeologist
					
									
    
	
    
	                                    
                      
    
                        
                          Guru
                        19935 points
                      
    
                          
                   		
		
    
					
    I am compiling c files and I am not using strict ANSI mode.
    

    The following compiler flags are used by my project:
    

    -v28 -ml -mt --float_support=fpu32 -Ooff --opt_for_speed=5  --diag_warning=225 --gen_func_subsections=on --asm_listing 
    

    Stephen
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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						in reply to stevenh
					
									
    
	
    
	                                    
                      
    
                        
                          TI__Guru*
                        84225 points
                      
    
                          
                   		
		
    
					
    The C standard says that "signed char", "unsigned char", and plain "char" are three distinct types.  The type plain "char" has different semantics than "signed char", even for architectures where plain "char" has exactly the same representation as "signed char."  This is in contrast to plain "int", which is exactly "signed int".
    

    The notion of "compatible types" is a lot more strict in C that you'd expect; even though "signed char" and plain "char" have the same representation, they are not compatible because they are not the same type.
    

    When calling strncpy, since you're using a cast anyway, you should cast directly to the type that strncpy expects.
    

    You can safely ignore this warning in this case, but it will become an error if you use strict ANSI mode.
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                 	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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