6.32 Mixed Declarations, Labels and Code

ISO C99 and ISO C++ allow declarations and code to be freely mixed within compound statements. ISO C2X allows labels to be placed before declarations and at the end of a compound statement. As an extension, GNU C also allows all this in C90 mode. For example, you could do:

int i;
/* … */
i++;
int j = i + 2;

Each identifier is visible from where it is declared until the end of the enclosing block.