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8360941: [ubsan] MemRegion::end() shows runtime error: applying non-zero offset 8388608 to null pointer #26216

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8360941: [ubsan] MemRegion::end() shows runtime error: applying non-zero offset 8388608 to null pointer #26216

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e2407fd
JDK-8360941
MBaesken Jul 9, 2025
d31a4f3
Change the test, avoid using address 0
MBaesken Jul 16, 2025
850e92d
blank
MBaesken Jul 16, 2025
f325d87
blank
MBaesken Jul 16, 2025
842077a
Avoid assertions, align address in test
MBaesken Jul 17, 2025
f0888ce
Simplify test coding
MBaesken Jul 18, 2025
0a9adaa
Suggestion by Thomas Stuefe
MBaesken Jul 21, 2025
53d20a2
Alignment
MBaesken Jul 22, 2025
bf78338
Adjust alignment and freeing
MBaesken Jul 22, 2025
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6 changes: 5 additions & 1 deletion test/hotspot/gtest/gc/g1/test_freeRegionList.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,11 @@ TEST_OTHER_VM(G1FreeRegionList, length) {

// Create a fake heap. It does not need to be valid, as the G1HeapRegion constructor
// does not access it.
MemRegion heap(nullptr, num_regions_in_test * G1HeapRegion::GrainWords);
int val = 1;
HeapWord* ptr = reinterpret_cast<HeapWord*>(&val);
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The initial value for val doesn't matter, since we're using its address rather than value.
And the cast could be removed by changing the type of val, leading to something like this:

HeapWord val{};
HeapWord* ptr = align_up(&val, os::vm_page_size());

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I adjusted the coding .

ptr = align_up(ptr, os::vm_page_size());

MemRegion heap(ptr, num_regions_in_test * G1HeapRegion::GrainWords);

// Allocate a fake BOT because the G1HeapRegion constructor initializes
// the BOT.
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