How to mix hexadecimal char and normal char in string literal in C++?

Question

Is it possible to mix '\xfd' and 'a' in a single string literal? For example:

unsigned char buff1[] = "\xfda";

unsigned char buff1[] = "\x0f\x0015899999999";

VC++2015 reports:

Error C2022 '-1717986919': too big for character

@slava that dupe doesn't answers the question. The OP is asking how to have the chars `'\xfd'` and `'a'` in a string one after the other. — NathanOliver, Aug 01 '18 at 14:56
-1717986919 is 0x99999999 @Osiris you should post it as an answer — phuclv, Aug 01 '18 at 15:02
This question [here](https://stackoverflow.com/q/47571520/509868) is also close. — anatolyg, Aug 01 '18 at 15:03
probably a better dupe: [Tell where escaped hexadecimal ends in a string](https://stackoverflow.com/q/31239524/995714) — phuclv, Aug 01 '18 at 15:09

NathanOliver · Answer 1 · 2018-08-01T15:07:47.210

You will not be able to do so using a hex character literal in a single string. [lex.ccon]/8 states

The escape \ooo consists of the backslash followed by one, two, or three octal digits that are taken to specify the value of the desired character. The escape \xhhh consists of the backslash followed by x followed by one or more hexadecimal digits that are taken to specify the value of the desired character. There is no limit to the number of digits in a hexadecimal sequence. A sequence of octal or hexadecimal digits is terminated by the first character that is not an octal digit or a hexadecimal digit, respectively. The value of a character literal is implementation-defined if it falls outside of the implementation-defined range defined for char (for character literals with no prefix) or wchar_t (for character literals prefixed by L). [ Note: If the value of a character literal prefixed by u, u8, or U is outside the range defined for its type, the program is ill-formed. — end note ]

^{emphasis mine}

This means '\xfda' is considered a single hex character literal since all of its digits are valid hex digits. What you can do is use multiple string literals that will be concatenated for you to break it up like

unsigned char buff1[] = "\xfd" "a";

Another option would be to switch to using an octal literal if you want 'a' to be part of the string. That would be "\375a".

score 2 · Accepted Answer · answered Aug 01 '18 at 15:07

As mentioned by the other answer '\xfda' is considered as a single hex character literal. To get a string literal with '\xfd' and 'a' you need to split the string.

"\xfd" "a"

Adjacent string literal tokens are concatenated, which means that for example "ab" "cd" is the same as "abcd".

score 0 · Answer 3 · answered Aug 01 '18 at 15:08

0

Not possible, as explained well in NathanOliver's answer. But there is also no need you can simply use two literals:

unsigned char buff1[] = "\x0f\x00""15899999999";

answered Aug 01 '18 at 15:08

eerorika

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How to mix hexadecimal char and normal char in string literal in C++?

3 Answers3