Why is conversion from string constant to char valid in C but invalid in C

Question

The C  11 Standard  ISO IEC 14882 2011  says in    C 1 1   char  p    abc      valid in C  invalid in C     For the C   it s OK as a pointer to a String Literal is harmful since any attempt to modify it leads to a crash  But why is it valid in C   The C  11 says also   char  p    char   abc      OK  cast added   Which means that if a cast is added to the first statement it becomes valid   Why does the casting makes the second statement valid in C   and how is it different from the first one  Isn t it still harmful  If it s the case  why did the standard said that it s OK

User · Answer

You can declare like one of the below options  char data      quot Testing String quot    or const char  data    quot Testing String quot    or char  data    char    quot Testing String quot

User · Answer

It s valid in C for historical reasons  C traditionally specified that the type of a string literal was char   rather than const char    although it qualified it by saying that you re not actually allowed to modify it   When you use a cast  you re essentially telling the compiler that you know better than the default type matching rules  and it makes the assignment OK

User · Answer

You can also use strdup   char  p   strdup  abc

User · Answer

Up through C  03  your first example was valid  but used a deprecated implicit conversion--a string literal should be treated as being of type char const    since you can t modify its contents  without causing undefined behavior    As of C  11  the implicit conversion that had been deprecated was officially removed  so code that depends on it  like your first example  should no longer compile   You ve noted one way to allow the code to compile  although the implicit conversion has been removed  an explicit conversion still works  so you can add a cast  I would not  however  consider this  fixing  the code   Truly fixing the code requires changing the type of the pointer to the correct type   char const  p    abc      valid and safe in either C or C      As to why it was allowed in C    and still is in C   simply because there s a lot of existing code that depends on that implicit conversion  and breaking that code  at least without some official warning  apparently seemed to the standard committees like a bad idea

[c++] Why is conversion from string constant to 'char*' valid in C but invalid in C++

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