From b2f9ac4fb5d5a79515b9f905bf76a493b301fad3 Mon Sep 17 00:00:00 2001
From: Gus Smith <guscomps@gmail.com>
Date: Fri, 6 Feb 2026 18:18:03 -0800
Subject: [PATCH] Check for dimacs nullptr on file creation+fn call

---
 libs/ezsat/ezcmdline.cc | 3 +++
 libs/ezsat/ezsat.cc     | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/libs/ezsat/ezcmdline.cc b/libs/ezsat/ezcmdline.cc
index 2eef1b06d..57800591c 100644
--- a/libs/ezsat/ezcmdline.cc
+++ b/libs/ezsat/ezcmdline.cc
@@ -14,6 +14,9 @@ bool ezCmdlineSAT::solver(const std::vector<int> &modelExpressions, std::vector<
 	const std::string cnf_filename = Yosys::stringf("%s/problem.cnf", tempdir_name.c_str());
 	const std::string sat_command = Yosys::stringf("%s %s", command.c_str(), cnf_filename.c_str());
 	FILE *dimacs = fopen(cnf_filename.c_str(), "w");
+	if (dimacs == nullptr) {
+		Yosys::log_cmd_error("Failed to create CNF file `%s`.\n", cnf_filename.c_str());
+	}
 
 	std::vector<int> modelIdx;
 	for (auto id : modelExpressions)
diff --git a/libs/ezsat/ezsat.cc b/libs/ezsat/ezsat.cc
index 69a59c8cd..8e3114705 100644
--- a/libs/ezsat/ezsat.cc
+++ b/libs/ezsat/ezsat.cc
@@ -1224,6 +1224,11 @@ ezSATvec ezSAT::vec(const std::vector<int> &vec)
 
 void ezSAT::printDIMACS(FILE *f, bool verbose, const std::vector<std::vector<int>> &extraClauses) const
 {
+	if (f == nullptr) {
+		fprintf(stderr, "Usage error: printDIMACS() must not be called with a null FILE pointer\n");
+		abort();
+	}
+
 	if (cnfConsumed) {
 		fprintf(stderr, "Usage error: printDIMACS() must not be called after cnfConsumed()!\n");
 		abort();