Fix Proto encoding of negative integers #889
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apangin
reviewed
Feb 7, 2024
src/converter/one/proto/Proto.java
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| @@ -71,7 +71,7 @@ public void writeInt(int n) { | |||
| int length = n == 0 ? 1 : (38 - Integer.numberOfLeadingZeros(n)) / 7; | |||
| ensureCapacity(length); | |||
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| while (n > 0x7f) { | |||
| while (n & 0x7f != n) { | |||
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Why can a number be negative? In what cases?
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The case I hit was nanosSinceLastSample in jfr2pprof.java being negative.
I don't know if that is supposed to happen; all I can tell you is that it happened, with async-profiler 3.0 and the default clock source.
src/converter/one/proto/Proto.java
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| @@ -82,7 +82,7 @@ public void writeLong(long n) { | |||
| int length = n == 0 ? 1 : (70 - Long.numberOfLeadingZeros(n)) / 7; | |||
| ensureCapacity(length); | |||
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| while (n > 0x7f) { | |||
| while (n & 0x7f != n) { | |||
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A canonical way to check if an integer has higher bits set is
(n & ~0x7f) != 0
or
(n >>> 7) != 0
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I changed the check based on your suggestion.
cklin
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Thank you for the fix. Merged. |
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Currently the
Protoclass determines whether to emit a continuing byte for the integer valuenthis way:The intention of the comparison is to check whether
nhas any bit set below the lowest 7 bits. Unfortunately it does not work ifnis negative, which causes the loop to be skipped entirely. When that happens, thejfr2pprofproduces a protobuf profile that is rejected bypprof.This PR fixes the bug so that
Protoencodes negative integer values correctly.