Creating array using emx array api with initialization to zero
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I have MATLAB Coder project which contains emx arrays.
When I generate C code in MATLAB R2021a, Coder generates emxCreate function with calloc inside:
emxArray_Nodes *emxCreateND_Nodes(int numDimensions, const int *size)
{
emxArray_Nodes *emx;
int numEl;
emxInit_Nodes(&emx, numDimensions);
numEl = 1;
for (int i = 0; i < numDimensions; i++) {
numEl *= size[i];
emx->size[i] = size[i];
}
emx->data = (Nodes *)calloc(static_cast<unsigned int>(numEl), sizeof(Nodes));
emx->numDimensions = numDimensions;
emx->allocatedSize = numEl;
return emx;
}
But when I generate C code in MATLAB R2023b, Coder generates emxCreate funciotn with malloc:
emxArray_Nodes *emxCreateND_Nodes(int numDimensions, const int *size)
{
emxArray_Nodes *emx;
int numEl;
emxInit_Nodes(&emx, numDimensions);
numEl = 1;
for (int i = 0; i < numDimensions; i++) {
numEl *= size[i];
emx->size[i] = size[i];
}
emx->data = static_cast<Nodes *>(
malloc(static_cast<unsigned int>(numEl) * sizeof(Nodes)));
emx->numDimensions = numDimensions;
emx->allocatedSize = numEl;
return emx;
}
In the second code memory for my struct arrays is allocated without initialization to zero. As a result, after updating MATLAB, code behaviour was changed.
How can I force MATLAB Coder R2023b to generate emx Create functions with calloc inside for initialization all struct array elements with zeros?
采纳的回答
Ezra Stein
2024-3-18
1 个投票
Hi Dmitri,
In R2023b we began generating emxArray allocation functions without zero-initializing their data. This was done as a performance enhancement because the generated code never actually relied on the zero-initialized data internally. Unfortunately, there is currently no way to enable the old behavior.
However, there are two possible workarounds:
- Manually initialize the data to 0 after creating the emxArray. This is the simplest approach but it incurs the preformance overhead of doing an allocation followed by a zero-initialization.
- Allocate memory via calloc manually, then wrap that memory in an emxArray using the emxCreateWrapper_<name> or emxCreateWrapperND_<name> utility functions. More details about this workflow can be found in the documentation here: https://www.mathworks.com/help/coder/ug/use-c-arrays-in-the-generated-function-interfaces.html#mw_1bf6258f-c070-4743-bb63-500d05e4542e
I am aware that the linked documentation page still states that the emxArray creation functions zero initialize the data. As a result, users have been relying on this behavior with an expectation that it will not change without warning. I am sorry for the inconvenience that this breaking change has caused.
I will discuss with our team to consider an enhancement that would allow users to enable the old behavior if desired.
Best,
-Ezra
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