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What is proper test for endianness?
Create an integer, and read its first byte (least significant byte). If that byte is 1, then the system is little endian, otherwise it’s big endian. This does not answer the question; it’s a runtime check, not a compiletime check.
Does Endianness affect performance?
If it fetches the least significant byte first, it can start doing the addition while the most significant byte is being fetched from memory. This parallelism is why performance is better in little endian on such as system.
Should I use big or little endian?
This is called endianness and it refers to the ordering of the bytes. Specifically, little-endian is when the least significant bytes are stored before the more significant bytes, and big-endian is when the most significant bytes are stored before the less significant bytes.
How to determine the endianness of a compiler?
If you can’t find what predefined macros your compiler uses from its documentation, you can also try coercing it to spit out its full list of predefined macros and guess from there what will work (look for anything with ENDIAN, ORDER, or the processor architecture name in it).
Can a runtime check replace an endian check?
If everything works correctly, then this code can replace any runtime checks that either I or anyone else uses for endian checking.
How to check the endianness of a string?
At run-time, you can do trivial checks such as setting a multi-byte value to a known bit string and inspect what bytes that results in. For instance using a union, Please note that for completely portable endianness checks, you need to take into account both big-endian, little-endian and mixed-endian systems.
Do you have to use compiler macros to check endianness?
You have to use predefined compiler macros ( \\__BIG_ENDIAN__ or \\__LITTLE_ENDIAN__ with clang, or \\__BYTE_ORDER__ with gcc). The other compiler macro tricks mentioned will only detect the endianness of the architecture you are compiling on, not the endianness of the architecture you are compiling for, so something like this is wrong: