linux - strange macro in c, using multiple statements -

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• are compound statements (blocks) surrounded parens expressions in ansi c? 2 answers

i found strange syntax while reading linux source code. container_of macro looks like

#define container_of(ptr, type, member) ({                      \         const typeof( ((type *)0)->member ) *__mptr = (ptr);    \         (type *)( (char *)__mptr - offsetof(type,member) );}) 

what confused me syntax ({statement1; statement2;})

i tried simple code like

int = {1;2;}; 

i compiled gcc. after running, 'a' seemed 2. couldn't compiled microsoft vc++. syntax expanded feature of gcc? if so, how can same effect without gcc expansion, define multiple statements , return value using macro?

the ({...}) syntax gcc extension, called statement expressions.

the typeof gcc extension.

both extensions available in other compilers, llvm/clang (or tinycc).

the linux kernel uses them quite often.

it quite difficult avoid them. if wanted to, might consider (and non trivial task), conversion gimple low-level, non-portable , unreadable c. might use melt (part of job done in file melt/xtramelt-c-generator.melt j.salvucci).