add test for pisharedmemory

tests/io/testpisharedmemory.cpp

@@ -0,0 +1,35 @@
+#include "pisharedmemory.h"
+
+#include "gtest/gtest.h"
+
+#ifdef WINDOWS
+#  include <process.h>
+#else
+#  include <unistd.h>
+#endif
+
+TEST(PISharedMemory_Test, ReadWriteBounds) {
+	PISharedMemory shm("pip_bughunt_shm_bounds_" + PIString::fromNumber(int(getpid())), 64);
+	ASSERT_TRUE(shm.open());
+
+	const char payload[32] = "0123456789abcdef";
+	ASSERT_EQ(32, shm.write(payload, 32));
+	ASSERT_EQ(16, shm.write(payload, 16, 10));
+
+	// Out-of-bounds writes must be rejected, not silently overflow the mapping.
+	EXPECT_EQ(-1, shm.write(payload, 100));    // exceeds size
+	EXPECT_EQ(-1, shm.write(payload, 32, 97)); // offset + size exceeds size
+	EXPECT_EQ(-1, shm.write(payload, 16, -5)); // negative offset
+
+	// Out-of-bounds reads must be rejected.
+	char dst[128];
+	EXPECT_EQ(-1, shm.read(dst, 200));    // exceeds size
+	EXPECT_EQ(-1, shm.read(dst, 32, 97)); // offset + size exceeds size
+	EXPECT_EQ(-1, shm.read(dst, 32, -1));
+
+	// In-bounds reads must still succeed.
+	EXPECT_EQ(16, shm.read(dst, 16, 10));
+	ASSERT_EQ(0, memcmp(dst, "0123456789abcdef", 16));
+
+	ASSERT_TRUE(shm.close());
+}