Validate cuOptGetErrorString buffer size

[fallintoplace]

This tightens one C API edge case and adds a small regression test for it.

What changed:

• reject non-positive buffer sizes in cuOptGetErrorString
• add a focused C API test that checks 0 and -1 buffer sizes

Why:
cuOptGetParameter already rejects <= 0 output buffer sizes, but cuOptGetErrorString was still passing its signed size straight into snprintf. This just makes the behavior consistent and keeps the validation on the API boundary.

Testing:

• git diff --check
• not run here: this machine does not have nvcc or a configured cuOpt build environment, so I could not build libcuopt / run C_API_TEST locally

Closes #1311.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

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Plan: Enterprise

Run ID: 340e3704-8491-4047-9983-b3fcd2e1f65d

📥 Commits

Reviewing files that changed from the base of the PR and between 86268f2 and f42ac18.

📒 Files selected for processing (3)

• cpp/include/cuopt/linear_programming/cuopt_c.h
• cpp/src/pdlp/cuopt_c.cpp
• cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp

✅ Files skipped from review due to trivial changes (1)

• cpp/include/cuopt/linear_programming/cuopt_c.h

🚧 Files skipped from review as they are similar to previous changes (1)

• cpp/src/pdlp/cuopt_c.cpp

---

📝 Walkthrough

Walkthrough

This PR adds input validation to the cuOptGetErrorString C API function to reject non-positive buffer sizes, updates the corresponding documentation, and introduces a test verifying the new validation behavior alongside successful error string retrieval with valid buffers.

Changes

Error String Buffer Size Validation

Layer / File(s)	Summary
Implementation: buffer size validation in cuOptGetErrorString cpp/src/pdlp/cuopt_c.cpp, cpp/include/cuopt/linear_programming/cuopt_c.h	Added an early-return guard in cuOptGetErrorString to return CUOPT_INVALID_ARGUMENT when error_string_size <= 0. Updated Doxygen documentation for the error_string_size parameter to state "Must be positive."
Test coverage for invalid buffer sizes cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp	Added test(c_api, error_string_invalid_buffer_size) that constructs a solution with a ValidationError, calls cuOptGetErrorString with invalid sizes (0, -1) expecting CUOPT_INVALID_ARGUMENT, and with a valid buffer expecting CUOPT_SUCCESS and the error message "validation failed". Includes cuopt/error.hpp to access error types.

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Validate cuOptGetErrorString buffer size' accurately describes the main change in the pull request, which is adding validation for the buffer size parameter.
Description check	✅ Passed	The description clearly explains what changed, why it was necessary, and references the related issue #1311. It is directly related to the changeset.
Linked Issues check	✅ Passed	The pull request fully addresses all coding objectives from issue #1311: adds validation to reject error_string_size <= 0, prevents passing non-positive sizes to snprintf, and includes a regression test for both 0 and -1 buffer sizes.
Out of Scope Changes check	✅ Passed	All changes are in scope and directly address the objectives from issue #1311. The modifications to cuopt_c.cpp, cuopt_c.h documentation, and the new test are all focused on the buffer size validation requirement.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 Infer (1.2.0)

cpp/src/pdlp/cuopt_c.cpp

cpp/src/pdlp/cuopt_c.cpp:8:10: fatal error: 'cuopt/linear_programming/cuopt_c.h' file not found
8 | #include <cuopt/linear_programming/cuopt_c.h>
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
Aborting translation of method 'cuOptAddQuadraticConstraint' in file 'cpp/src/pdlp/cuopt_c.cpp': "Assert_failure src/clang/cAst_utils.ml:249:53"
Uncaught Internal Error: "Assert_failure src/clang/cAst_utils.ml:249:53"
Error backtrace:
Raised at ClangFrontend__CAst_utils.get_decl_from_typ_ptr in file "src/clang/cAst_utils.ml", line 249, characters 53-65
Called from ClangFrontend__CTrans.CTrans_funct.get_destructor_decl_ref in file "src/clang/cTrans.ml", line 658, characters 12-59
Called from ClangFrontend__CTrans.CTrans_funct.destructor_calls.(fun) in file "src/clang/cTrans.ml", line 2048, characters 12-69
Called from Base__List.rev_filter_map.loop in file "src/list.ml", line 944, characters 13-17
Called from Base__List.filter_map in file "src/list.ml" (inlined), line

... [truncated 2200 characters] ...

ClangFrontend__CTrans.CTrans_funct.instruction_insert_cxx_temporary_markers in file "src/clang/cTrans.ml", line 4866, characters 22-60
Called from ClangFrontend__CTrans.CTrans_funct.instruction_scope in file "src/clang/cTrans.ml", line 4850, characters 22-79
Called from ClangFrontend__CTrans.CTrans_funct.instruction_log.(fun) in file "src/clang/cTrans.ml", line 4782, characters 12-47
Re-raised at IStdlib__IExn.reraise_after in file "src/istd/IExn.ml" (inlined), line 13, characters 2-50
Called from ClangFrontend__CTrans.CTrans_funct.instruction_log.(fun) in file "src/clang/cTrans.ml", line 4784, characters 10-1023
Called from ClangFrontend__CTrans.CTrans_funct.instruction in file "src/clang/cTrans.ml" (inlined), line 4765, characters 38-71
Called from ClangFrontend__CTrans.CTrans_funct.exec

cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp

In file included from cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp:8:
cpp/tests/linear_programming/c_api_tests/c_api_tests.h:8:10: fatal error: 'cuopt/linear_programming/cuopt_c.h' file not found
8 | #include <cuopt/linear_programming/cuopt_c.h>
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp:529:1-551:1: ERROR translating statement 'CompoundStmt'
Aborting translation of method 'anonymous_namespace_cpp_tests_linear_programming_c_api_tests_c_api_tests.cpp::tcp_connect_check' in file 'cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp': "Assert_failure src/clang/cAst_utils.ml:249:53"
Uncaught Internal Error: "Assert_failure src/clang/cAst_utils.ml:249:53"
Error backtrace:
Raised at ClangFrontend__CAst_utils.get_decl_from_typ_ptr in file "src/clang/cAst_utils.ml", line 249, characters 53-65
Called from ClangFrontend__CTrans.CTrans_funct.get_destructor_decl_ref in file "src/clang/cTrans.

... [truncated 2200 characters] ...

file "src/istd/IExn.ml" (inlined), line 18, characters 15-63
Called from ClangFrontend__CFrontend_errors.protect in file "src/clang/cFrontend_errors.ml", line 48, characters 6-141
Called from ClangFrontend__CFrontend_decl.CFrontend_decl_funct.add_method in file "src/clang/cFrontend_decl.ml" (inlined), line 54, characters 4-52
Called from ClangFrontend__CFrontend_decl.CFrontend_decl_funct.function_decl in file "src/clang/cFrontend_decl.ml", line 90, characters 12-151
Called from ClangFrontend__CFrontend_decl.CFrontend_decl_funct.translate_one_declaration in file "src/clang/cFrontend_decl.ml", line 453, characters 10-56
Called from ClangFrontend__CFrontend_decl.CFrontend_decl_funct.translate_one_declaration.translate in file "src/clang/cFrontend_decl.ml" (inlined), line 448, characters 24-9

---

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[github-actions]

🔔 Hi @anandhkb, this pull request has had no activity for 7 days. Please update or let us know if it can be closed. Thank you!

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[nguidotti]

/ok to test bd69111