Fix error string buffer size validation

[Rohithmatham12]

Summary

• Reject non-positive error_string_size in cuOptGetErrorString before calling snprintf.
• Add C API regression coverage for zero and negative buffer sizes using a valid CPU-backed solution handle.
• Clarify that the error string buffer size must be positive.

Fixes #1311.

Testing

• /opt/homebrew/opt/llvm/bin/clang-format -i cpp/src/pdlp/cuopt_c.cpp cpp/include/cuopt/linear_programming/cuopt_c.h cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp
• git diff --check

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ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 515cd824-04b6-47d8-ba22-d34b9bee8c64

📥 Commits

Reviewing files that changed from the base of the PR and between 4284d91 and 92cc477.

📒 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/tests/linear_programming/c_api_tests/c_api_tests.cpp

---

📝 Walkthrough

Walkthrough

The PR adds input validation to the C API function cuOptGetErrorString to reject non-positive error_string_size values. The implementation now returns CUOPT_INVALID_ARGUMENT when buffer size is zero or negative. Documentation and test coverage have been added to reflect this behavior.

Changes

Input Validation for cuOptGetErrorString

Layer / File(s)	Summary
Input validation implementation and test coverage 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	Doxygen documentation for cuOptGetErrorString is updated to explicitly document that error_string_size must be positive. Implementation adds an early guard to return CUOPT_INVALID_ARGUMENT when error_string_size <= 0. Test includes were added and a new gtest verifies rejection of zero and negative buffer sizes and success with a valid buffer size.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 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 'Fix error string buffer size validation' directly and concisely describes the main change: adding validation for the error_string_size parameter in cuOptGetErrorString before calling snprintf.
Description check	✅ Passed	The description is clearly related to the changeset, explaining the summary of changes (validation addition, test coverage, documentation clarification) and referencing the linked issue #1311.
Linked Issues check	✅ Passed	The PR fully addresses all coding requirements from issue #1311: validates error_string_size <= 0 in cuOptGetErrorString [#1311], adds C API regression tests for zero and negative buffer sizes [#1311], and clarifies buffer size must be positive in documentation [#1311].
Out of Scope Changes check	✅ Passed	All changes are in-scope: the validation logic in cuopt_c.cpp, documentation update in cuopt_c.h, and test additions in c_api_tests.cpp directly address the requirements from issue #1311 without introducing unrelated modifications.

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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:526:1-548:1: 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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[nguidotti]

There is a similar fix in #1313. Although the test case here seems better.

[nguidotti]

/ok to test 4284d91