fix: memory safety bugs in AxBRowIP.c and add CMakeLists.txt#3
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piyush0028 wants to merge 1 commit into
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fix: memory safety bugs in AxBRowIP.c and add CMakeLists.txt#3piyush0028 wants to merge 1 commit into
piyush0028 wants to merge 1 commit into
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- Replace malloc with calloc for cD_ accumulator (Bug 1: UB from uninitialised memory causing incorrect SpGEMM results) - Add free(cD_) inside row loop (Bug 2: leaked N*4 bytes per row) - Replace density-based cNNZ estimate with safe M*N upper bound (Bug 3: underestimate caused out-of-bounds writes to cD/cC) - Fix accumulator size from K to N (Bug 4: wrong for non-square A*B) - Add CMakeLists.txt so project compiles with standard cmake/make
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Summary
This PR fixes four memory safety bugs in
src/matmul/AxBRowIP.cand adds aCMakeLists.txtso the project can be compiled with the standardcmake .. && makeworkflow.Bugs Fixed
Bug 1 - undefined behaviour (malloc → calloc)
The per-row dense accumulator
cD_was allocated withmalloc, leaving garbage values in memory. EverycD_[idx] += valA valBwas accumulating onto uninitialised data, producing incorrect SpGEMM results. Fixed by replacing withcalloc, which zero-initialises.Bug 2 - memory leak
cD_was allocated inside the row loop but never freed. For a matrix with M rows this leaks N×4 bytes × M iterations gigabytes for large inputs. Fixed by addingfree(cD_)at the end of each row iteration.Bug 3 - buffer overflow in output allocation
cNNZ_estimationused a density formula that can return a value smaller than the actual output NNZ, causingcD[row_count]andcC[row_count]to write past the end of their arrays (silent out-of-bounds write). Replaced withsafe_cNNZ(M, N) = M * N, which is always a valid upper bound. A symbolic pre-count pass can be added later to get exact NNZ cheaply.Bug 4 - accumulator sized K instead of N
The accumulator
cD_was sizedK(columns of A), but it is indexed by output column (0..N-1). For non-square A×B this is incorrect. Fixed to use N.Added
CMakeLists.txttargeting C11/C++17 with-Wall -Wextra -O3Tested
Compiled cleanly with GCC 11.4.0 and CMake 3.22.1 on Ubuntu 22.04 with zero errors and zero warnings.