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Decr pc when looking for DWARF loc list entry mid-stack
When looking for a variable location in a DWARF location list, we search the list of ranges to find one that includes the pc. With a function mid-stack, the "pc" is the return pc instead of the call instruction, and in optimized code this can be another function or a different basic block (with different variable locations). Back up the "pc" value mid-stack to find the correct location list entry. Differential Revision: https://reviews.llvm.org/D124597 rdar://63903416
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C_SOURCES := main.c | ||
CFLAGS_EXTRAS := -O1 | ||
include Makefile.rules |
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lldb/test/API/functionalities/location-list-lookup/TestLocationListLookup.py
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"""Test that lldb picks the correct DWARF location list entry with a return-pc out of bounds.""" | ||
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import lldb | ||
from lldbsuite.test.decorators import * | ||
from lldbsuite.test.lldbtest import * | ||
from lldbsuite.test import lldbutil | ||
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class LocationListLookupTestCase(TestBase): | ||
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mydir = TestBase.compute_mydir(__file__) | ||
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def setUp(self): | ||
# Call super's setUp(). | ||
TestBase.setUp(self) | ||
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def test_loclist(self): | ||
self.build() | ||
exe = self.getBuildArtifact("a.out") | ||
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# Create a target by the debugger. | ||
target = self.dbg.CreateTarget(exe) | ||
self.assertTrue(target, VALID_TARGET) | ||
self.dbg.SetAsync(False) | ||
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li = lldb.SBLaunchInfo(["a.out"]) | ||
error = lldb.SBError() | ||
process = target.Launch(li, error) | ||
self.assertTrue(process.IsValid()) | ||
self.assertTrue(process.is_stopped) | ||
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# Find `main` on the stack, then | ||
# find `argv` local variable, then | ||
# check that we can read the c-string in argv[0] | ||
for f in process.GetSelectedThread().frames: | ||
if f.GetDisplayFunctionName() == "main": | ||
argv = f.GetValueForVariablePath("argv").GetChildAtIndex(0) | ||
strm = lldb.SBStream() | ||
argv.GetDescription(strm) | ||
self.assertNotEqual(strm.GetData().find('a.out'), -1) |
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#include <stdio.h> | ||
#include <stdlib.h> | ||
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// The goal with this test is: | ||
// 1. Have main() followed by foo() | ||
// 2. Have the no-return call to abort() in main be the last instruction | ||
// 3. Have the next instruction be the start of foo() | ||
// 4. The debug info for argv uses a location list. | ||
// clang at -O1 on x86_64 or arm64 has debuginfo like | ||
// DW_AT_location (0x00000049: | ||
// [0x0000000100003f15, 0x0000000100003f25): DW_OP_reg4 RSI | ||
// [0x0000000100003f25, 0x0000000100003f5b): DW_OP_reg15 R15) | ||
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void foo(int); | ||
int main(int argc, char **argv) { | ||
char *file = argv[0]; | ||
char f0 = file[0]; | ||
printf("%c\n", f0); | ||
foo(f0); | ||
printf("%s %d\n", argv[0], argc); | ||
abort(); /// argv is still be accessible here | ||
} | ||
void foo(int in) { printf("%d\n", in); } |