Resource inclusion (since C++26)

 

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Preprocessor

#if#ifdef#ifndef#else#elif#elifdef#elifndef#endif (C++23)(C++23)

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#line

#embed (C++26)

 

#embed is a preprocessor directive to include resources, where a resource is defined as a source of data accessible from the translation environment.

Syntax

#embed < resource > pp-tokens (optional) \n *	(1)
#embed " resource " pp-tokens (optional) \n *	(2)
#embed pp-tokens\n *	(3)
__has_embed ( pp-balanced-token-seq )	(4)

1) Searches for a uniquely identified resource.

2) Searches for a named resource. Fallbacks to (1) as if chevrons were used instead of quotes.

1-2) Replaces the directive by a comma separated list of integers corresponding to the data of the resource.

3) If neither (1) nor (2) is matched, pp-tokens will undergo macro replacement. The directive after replacement will be tried to match with (1) or (2) again.

resource	-	A resource to embed
pp-tokens	-	Positive number of preprocessing tokens
pp-balanced-token-seq	-

Explanation

1) A search takes place in a sequence of implementation-defined places. How the places are specified or the resource identified is implementation-defined.

2) A search takes place in an implementation-defined manner. A fallback follows if this search is not supported, or if the search fails.

Example

Assume the file word.txt contains a single word: worlds.

• limit(5) limits embeding to 5 characters (effectively embeding the word world without the leading leter s).
• prefix(0x2C, 0x20, ) prepends , ​ to the string s: 0x2C is a hex code of , and 0x20 is a hex code of ​ ​.
• suffix(, 0x21) appends !​ to the string s: 0x21 is a hex code of !.

Run this code

#include <string>
#include <print>
 
int main()
{
    std::string s
    {
        #embed "word.txt" prefix(0x2C, 0x20, ) suffix(, 0x21) limit(5)
    };
 
    std::println("Hello{}", s);
}

Possible output:

Hello, world!

References

• C++26 standard (ISO/IEC 14882:2026):

• 15.4 Resource inclusion [cpp.embed]

See also

• Source file inclusion

C documentation for Binary resource inclusion (since C23)