C style cast from unsigned char to const char

Question

I have   unsigned char  foo    std  string str  str append static cast lt const char  gt  foo        The error  invalid static cast from type    unsigned char     to type    const char      What s the correct way to cast here in C   style

User · Answer

Try reinterpret cast  unsigned char  foo    std  string str  str append reinterpret cast lt const char  gt  foo

User · Answer

Too many comments to make to different answers  so I ll leave another answer here   You can and should use reinterpret cast lt  gt   in your case  str append reinterpret cast lt const char  gt  foo        because  while these two are different types  the 2014 standard  chapter 3 9 1 Fundamental types  basic fundamental  says there is a relationship between them      Plain char  signed char and unsigned char are three distinct types  collectively called narrow character types  A char  a signed char  and an unsigned char occupy the same amount of storage and have the same alignment requirements  3 11   that is  they have the same object representation     selection is mine   Here s an available link  https   en cppreference com w cpp language types Character types  Using wchar t for Unicode multibyte strings is outdated  Should I use wchar t when using UTF-8

User · Answer

reinterpret cast

User · Answer

unsigned char  is basically a byte array and should be used to represent raw data rather than a string generally   A unicode string would be represented as wchar t   According to the C   standard a reinterpret cast between unsigned char  and char  is safe as they are the same size and have the same construction and constraints   I try to avoid reintrepret cast even more so than const cast in general   If static cast fails with what you are doing you may want to reconsider your design because frankly if you are using C   you may want to take advantage of what the  plus plus  part offers and use string classes and STL  aka std  basic string might work better for you

User · Answer

Hope it help       const unsigned attribName   getname    const unsigned attribVal   getvalue    const char  attrName NULL   attrVal NULL  attrName    const char   attribName  attrVal    const char   attribVal

User · Answer

You would need to use a reinterpret cast lt   as the two types you are casting between are unrelated to each other

User · Answer

char   and const unsigned char   are considered unrelated types  So you want to use reinterpret cast   But if you were going from const unsigned char  to a non const type you d need to use const cast first  reinterpret cast cannot cast away a const or volatile qualification

[c++] C++ style cast from unsigned char * to const char *

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