Simulink coder packed structs
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Hello, is there a way to have the Simulink autocoder turn bus objects into packed structs (byte alignment=1)? E.g., the struct definition might look like:
struct __attribute__((__packed__)) mystruct_A {
char a;
int b;
char c;
};
Thanks!
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回答（1 个）
Mark McBroom
2025-3-29
0 个投票
See the "Alignment" property for Simulink.Bus elements defined here: https://www.mathworks.com/help/simulink/slref/simulink.bus.html
Thanks.
Mark.
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Amin
2026-4-24，10:49
The Alignment property of Simulink.Bus does not make the generated C struct packed (byte-aligned). It only controls the alignment of the bus as a whole in memory, not the internal layout of its elements.
For example, even with Alignment = 1, the generated code is still of the form:
typedef struct {
real32_T a;
uint16_T b;
uint8_T c;
} MyStruct;
and the compiler may still insert padding between fields.
So this does not produce:
typedef struct __attribute__((__packed__)) {
...
} MyStruct;
As far as I understand, to achieve a truly packed layout with Simulink Coder, the only robust approaches are:
- Define the struct manually in a header with __attribute__((__packed__)) and set the bus to Imported, or
- Accept the generated struct layout and design the binary data to match the compiler’s padding.
If there is a way to force packed structs directly from Simulink Coder (e.g., via configuration or TLC), I would be very interested to know.
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