[Lldb-commits] [lldb] [lldb/linux] Make truncated reads work (PR #106532)

[Pavel Labath via lldb-commits]

================
@@ -0,0 +1,63 @@
+"""
+Test the memory commands operating on memory regions with holes
+"""
+
+import lldb
+from lldbsuite.test.lldbtest import *
+import lldbsuite.test.lldbutil as lldbutil
+from lldbsuite.test.decorators import *
+
+
+class MemoryHolesTestCase(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def setUp(self):
+        super().setUp()
+        # Find the line number to break inside main().
+        self.line = line_number("main.cpp", "// break here")
+
+    def _prepare_inferior(self):
+        self.build()
+        exe = self.getBuildArtifact("a.out")
+        self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
+
+        # Break in main() after the variables are assigned values.
+        lldbutil.run_break_set_by_file_and_line(
+            self, "main.cpp", self.line, num_expected_locations=1, loc_exact=True
+        )
+
+        self.runCmd("run", RUN_SUCCEEDED)
+
+        # The stop reason of the thread should be breakpoint.
+        self.expect(
+            "thread list",
+            STOPPED_DUE_TO_BREAKPOINT,
+            substrs=["stopped", "stop reason = breakpoint"],
+        )
+
+        # The breakpoint should have a hit count of 1.
+        lldbutil.check_breakpoint(self, bpno=1, expected_hit_count=1)
+
+        # Avoid the expression evaluator, as it can allocate allocate memory
+        # inside the holes we've deliberately left empty.
+        self.memory = self.frame().FindVariable("mem_with_holes").GetValueAsUnsigned()
+        self.pagesize = self.frame().FindVariable("pagesize").GetValueAsUnsigned()
+        positions = self.frame().FindVariable("positions")
+        self.positions = [
+            positions.GetChildAtIndex(i).GetValueAsUnsigned()
+            for i in range(positions.GetNumChildren())
+        ]
+        self.assertEqual(len(self.positions), 5)
+
+    @expectedFailureWindows
+    def test_memory_read(self):
+        self._prepare_inferior()
+
+        error = lldb.SBError()
+        content = self.process().ReadMemory(self.memory, 2 * self.pagesize, error)
+        self.assertEqual(len(content), self.pagesize)
+        self.assertEqual(content[0:7], b"needle\0")
+        self.assertTrue(error.Fail())
+        self.assertEqual(
+            f"memory read failed for {self.memory+self.pagesize:#x}", error.GetCString()
+        )
----------------
labath wrote:

I guess this kind of error behavior can be useful in some situations (you get the memory that can be read *and* the error for the part that cannot), but I've found it very counterintuitive to use. I'd definitely be open to changing that (returning an error only if we didn't read anything).

https://github.com/llvm/llvm-project/pull/106532