Questions tagged [packed]
78 questions
2
votes
3 answers
packed structs in tcc
I am trying to do packed struct in tcc C compiller.
Code is as follows and __attribute __ tag should be supported:
#include
#include
typedef struct _test_t{
char c;
uint16_t i;
char d;
}…
Nick
- 9,962
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- 80
2
votes
1 answer
__attribute__((packed)) and __attribute__((__packed__))
is there a difference between
__attribute__((__packed__)) and
__attribute__((packed))?
And if a struct is packed like this:
struct test { int a; short b; } __attribute__((__packed__)) there is never a need to use the packed attribute on each of…
user3035952
- 301
- 5
- 12
2
votes
1 answer
Switching between packed/unpacked structs
I have a lot of configuration data in EEPROM (4KB) which I read out in packed structures. Throughout my firmware I need to read/change these values very frequently, and performance of packed structures is not optimal, so I have a second struct which…
Maestro
- 9,046
- 15
- 83
- 116
1
vote
4 answers
How to construct a C struct/union with a very odd arrangement of bitfields?
I have the following layout of memory (pseudo code):
struct {
union {
fieldA : 45;
struct {
fieldB1 : 12;
fieldB2 : 33;
}
}
fieldC : 19;
}
i.e., the memory of field A can be sometimes…
RBH
- 11
- 2
1
vote
1 answer
replacing "__attribute__ ((packed))" for compact structures by a standard (portable) C method
Conversion of several values to a byte-string for radio transmission has to avoid unneeded bytes. Using GCC on an ARM target (32 bit) I use "attribute ((packed))". This directive is GCC based (as I read somewhere here) and so not generally portable…
peets
- 393
- 1
- 4
- 13
1
vote
3 answers
change bit size of packed struct in derived class
The existing code:
typedef unsigned int uint;
Class A
{
union xReg
{
uint allX;
struct
{
uint x3 : 9;
uint x2 : 9;
uint x1 : 14;
}__attribute__((__packed__))…
singleX
- 375
- 4
- 13
1
vote
2 answers
How do I interpret a python byte string coming from F1 2020 game UDP packet?
Title may be wildly incorrect for what I'm trying to work out.
I'm trying to interpret packets I am recieving from a racing game in a way that I understand, but I honestly don't really know what I'm looking at, or what to search to understand…
ninjaisfast
- 17
- 5
1
vote
0 answers
C: Address trap error when accessing a struct with odd no. of members
I am working with MPLABX with compiler xc16-gcc developing for the 16-bit dsPIC33CH128MP508 microcontroller. I am making code to read from RTC through I2C.
I have defined the following structs:
typedef struct tagRTC_VL_SECONDSBITS{
uint8_t…
Samah M. Nafie
- 11
- 2
1
vote
1 answer
How can I write packed BCD numbers to an old instrument (Varian FR41 Gaussmeter) with LabVIEW?
I am currently trying to communicate with an old instrument that uses packed BCD numbers only (it's a Varian FR41 Controller Gaussmeter if anyone is familiar). I am using LabVIEW to replicate some old C code that output the BCD code. Below is the C…
Jesse
- 244
- 2
- 15
1
vote
2 answers
Is signed type valid for each element using typedef + packed array (v.s. multidimensional packed array)
I have a question about signed property with multiple packed dimensions which is defined in stages with typedef.
Basically,
logic signed [1:0][2:0] foo;
* foo[0] is not signed (signed is meaningless if you expect signed element) because all entire…
Yunsung Mo
- 89
- 1
- 6
1
vote
3 answers
Packed structures and not packed without code repetition
I have this code:
// size probably 4 bytes
struct NotPacked
{
uint16_t first;
uint8_t second;
};
// size is 3 bytes
struct Packed
{
uint16_t first;
uint8_t second;
}__attribute__((packed));
I'd like to use the same structure,…
Saturnu
- 309
- 1
- 8
1
vote
0 answers
Using Emmet with pre-packed Ace
I'm trying to use Emmet with the pre-packed version of Ace in a single page.
`
bazooka07
- 23
- 2
1
vote
1 answer
Why some values make struct.pack and struct.unpack to fail on Windows?
When I use struct.pack() to convert a python integer to C structs (and write it to a file) and then struct.unpack() to reverse the conversion I get usually the original value...but not always. Why? Are there some unmanageable values?
Example:
import…
jlbmdm
- 188
- 6
1
vote
0 answers
gcc C++ explicit alignment gets lost if used through a reference parameter
The following code defines a packed (alignment 1) structure where the dwBug member is not aligned correctly. If such member is assigned to via means of a reference parameter, the assignemnt fails on architectures that do not support unaligned…
numo68
- 11
- 1
1
vote
1 answer
Getting embedded PACKED_STRUCT definition to compile under g++
I'm working on a smart meter project, ARM, keil compiler. I want to compile some of the more complex logic under g++ to run regression tests. I'm having a problem with some include files defining the interface to WMBus stack we…
Francis Cagney
- 301
- 1
- 10