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- Dictionarypacked/pakt/
adjective
- 1. (of a room, building, or other place) filled by a large number of people; very crowded: "they spoke to a packed auditorium at the Baltimore Museum"
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So if the code is intended to be generally portable, you may just have to define whatever packed structures you need in a platform-specific section of your header file. Or rather, structure your code so that a future port can do that if it has to.
1. When packed used during structure declaration, compiler will not add any padding to the members of the same structure. Below is the example code and output which is self explanatory. $ cat structure_packed.c. #include <stdio.h>. typedef struct __attribute__((__packed__)) {. char a; int ai;
Aug 29, 2014 · The gcc has introduced the __attribute__((packed)) precisely to avoid the dangerous effects you are seeking: the definition of the structure should binary compatible between all the user applications and libraries which use the same definition. But the gcc also provides a way to do the packing the old fashioned, dangerous way - #pragma pack ...
@DanielSantos: A quality compiler I use (Keil) recognizes "packed" qualifiers for pointers; if a structure is declared "packed", taking the address of a uint32_t member will yield a uint32_t packed*; trying to read from such a pointer on e.g. a Cortex-M0 will IIRC call a subroutine which will take ~7x as long as a normal read if the pointer is ...
Aug 2, 2012 · Data structure alignment is the way data is arranged and accessed in computer memory. It consists of two separate but related issues: data alignment and data structure padding. When a modern computer reads from or writes to a memory address, it will do this in word sized chunks (e.g. 4 byte chunks on a 32-bit system).
6. Padding and packing are just two aspects of the same thing: packing or alignment is the size to which each member is rounded off. padding is the extra space added to match the alignment. In mystruct_A, assuming a default alignment of 4, each member is aligned on a multiple of 4 bytes.
Mar 10, 2022 · 1. One effect (there are others) of applying the the packed attribute to a union is to remove any padding added at the end of the union. Here is a contrived example: #include <stdio.h>. typedef union carr {. char a[3]; short b; } Carr; typedef union __attribute__((packed)) parr {.
Apr 14, 2015 · The standard offers one extra alternative for writing pragmas: the _Pragma operator: #define PACKED_BEGIN _Pragma("pack(push, 1)") #define PACKED. #define PACKED_END _Pragma("pack(pop)") If the Borland compiler supports it, it should work. answered Apr 14, 2015 at 15:09. Angew is no longer proud of SO.
Jan 12, 2021 · IDK why that's called "unpack". – Peter Cordes. Oct 30, 2020 at 1:34. packed as in "packed together in a single register". extended packed seems to mean "extended to work with packed integers". "unpacked" is, IDK, maybe working with just the scalar or considering the register as a whole. – Margaret Bloom.
Aug 2, 2016 · error: types may not be defined in parameter types. error: typedef declaration invalid in parameter declaration. I can so no way around this other than by editing the include file to remove the PACKED_STRUCT. Obviously I won't edit the files directly, I'll copy them, edit them, and use the -I directive to make it find my modified files under G++.
