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@@ -0,0 +1,80 @@
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+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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+From: Primiano Tucci <[email protected]>
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+Date: Thu, 3 Oct 2019 16:24:52 +0100
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+Subject: metatrace: remove memset and trivial-ctor assumption
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+
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+Turns out that on MSVC std::atomic<int> is not trivially constructible
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+(although I think is still a plain old int, it just fails the check).
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+Fall back on resetting each element individually.
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+Thankfully the compiler can see through and eventually figures out
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+it can do a memset: https://godbolt.org/z/wMre8O
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+
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+Bug: chromium:1010616
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+Change-Id: I971ff888306d6bdbaf6e6b886f9ca506ddc1b30a
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+
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+diff --git a/include/perfetto/ext/base/metatrace.h b/include/perfetto/ext/base/metatrace.h
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+index 3858f68ec5eaf130aafa7d33f52a00e370395204..2c587c3fc63093f71a05e4c757def5c6384bf703 100644
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+--- a/include/perfetto/ext/base/metatrace.h
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++++ b/include/perfetto/ext/base/metatrace.h
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+@@ -116,22 +116,33 @@ struct Record {
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+ timestamp_ns_high = static_cast<uint16_t>(diff >> 32);
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+ }
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+
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++ // We can't just memset() this class because on MSVC std::atomic<> is not
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++ // trivially constructible anymore. Also std::atomic<> has a deleted copy
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++ // constructor so we cant just do "*this = Record()" either.
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++ // See http://bit.ly/339Jlzd .
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++ void clear() {
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++ this->~Record();
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++ new (this) Record();
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++ }
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++
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+ // This field holds the type (counter vs event) in the MSB and event ID (as
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+ // defined in metatrace_events.h) in the lowest 15 bits. It is also used also
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+ // as a linearization point: this is always written after all the other
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+ // fields with a release-store. This is so the reader can determine whether it
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+ // can safely process the other event fields after a load-acquire.
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+- std::atomic<uint16_t> type_and_id;
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++ std::atomic<uint16_t> type_and_id{};
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+
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+ // Timestamp is stored as a 48-bits value diffed against g_enabled_timestamp.
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+ // This gives us 78 hours from Enabled().
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+- uint16_t timestamp_ns_high;
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+- uint32_t timestamp_ns_low;
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++ uint16_t timestamp_ns_high = 0;
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++ uint32_t timestamp_ns_low = 0;
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+
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+- uint32_t thread_id;
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++ uint32_t thread_id = 0;
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+
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+ union {
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+- uint32_t duration_ns; // If type == event.
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++ // Only one of the two elements can be zero initialized, clang complains
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++ // about "initializing multiple members of union" otherwise.
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++ uint32_t duration_ns = 0; // If type == event.
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+ int32_t counter_value; // If type == counter.
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+ };
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+ };
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+diff --git a/src/base/metatrace.cc b/src/base/metatrace.cc
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+index 9ef2c68777c5d497d92b12d52df4df2454feda02..67d167c8d07bc8701d261c56d11ba17afcb6ec8a 100644
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+--- a/src/base/metatrace.cc
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++++ b/src/base/metatrace.cc
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+@@ -84,15 +84,9 @@ void Disable() {
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+
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+ // static
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+ void RingBuffer::Reset() {
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+- static_assert(PERFETTO_IS_TRIVIALLY_CONSTRUCTIBLE(Record) &&
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+- std::is_trivially_destructible<Record>::value,
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+- "Record must be trivial");
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+- // Cast pointers to void* to suppress "-Wclass-memaccess" from gcc, which
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+- // triggers as we're doing a raw memory set for a class (Record) that doesn't
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+- // have a copy assignment operator (due to the atomic |type_and_id|).
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+- memset(static_cast<void*>(records_.data()), 0, sizeof(records_));
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+- memset(static_cast<void*>(&bankruptcy_record_), 0,
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+- sizeof(bankruptcy_record_));
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++ bankruptcy_record_.clear();
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++ for (Record& record : records_)
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++ record.clear();
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+ wr_index_ = 0;
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+ rd_index_ = 0;
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+ has_overruns_ = false;
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Jaime Bernardo