Variable-Length Arrays (VLAs) Now Supported in emmtrix Studio
July 31, 2026
Not every valid C program is equally easy to analyze and optimize.
Variable-Length Arrays (VLAs) are a good example.
They make C code more expressive when array sizes depend on run-time information such as sensor input, message size, or configuration data. Instead of relying on fixed maximum dimensions, the array size can match the actual problem.
For analysis and optimization tools, however, this changes the picture.
The array extent becomes part of the program’s run-time state. Memory usage, loop bounds, data dependencies, and array accesses must therefore be analyzed with the run-time size in mind. Transformations such as parallelization and vectorization have to remain correct for every valid array extent.
Variable-Length Arrays are now supported in emmtrix Studio.
C applications using VLAs can now participate directly in the emmtrix analysis and optimization workflow without replacing VLAs with fixed-size buffers, introducing artificial maximum dimensions, or restructuring otherwise valid C code.
VLA support can also be combined with constant propagation. When an array size is known at a particular call site, emmtrix Studio can use that value to analyze and optimize the individual invocation with its actual array extent.
We explain the technical background, the analysis challenges, and the role of constant propagation in our Tech Wiki:
