As described in the FFI guide, you can add attributes to structs to use the same layout as C: #[repr(C)] struct Object { a: i32, // other members } and you also have the ability to pack the struct: #[repr(C, packed)] struct Object { a: i32, // other members } And for detecting that the … Read more
From the Linkers and loaders book: On 386 systems, the text base address is 0x08048000, which permits a reasonably large stack below the text while still staying above address 0x08000000, permitting most programs to use a single second-level page table. (Recall that on the 386, each second-level table maps 0x00400000 addresses.)
According to the C11 standard, the relational operators <, <=, >, and >= may only be used on pointers to elements of the same array or struct object. This is spelled out in section 6.5.8p5: When two pointers are compared, the result depends on the relative locations in the address space of the objects pointed … Read more
The .bss section is guaranteed to be all zeros when the program is loaded into memory. So any global data that is uninitialized, or initialized to zero is placed in the .bss section. For example: static int g_myGlobal = 0; // <— in .bss section The nice part about this is, the .bss section data … Read more
(Don’t apply these rules without thinking. See ESR’s point about cache locality for members you use together. And in multi-threaded programs, beware false sharing of members written by different threads. Generally you don’t want per-thread data in a single struct at all for this reason, unless you’re doing it to control the separation with a … Read more
It’s implementation-specific, but in practice the rule (in the absence of #pragma pack or the like) is: Struct members are stored in the order they are declared. (This is required by the C99 standard, as mentioned here earlier.) If necessary, padding is added between struct members, to ensure that the latter one uses the correct … Read more