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[XRay] [compiler-rt] stop writing garbage in naive log records
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Authored by pelikan on Jan 24 2018, 9:46 AM.

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Summary

Turns out sizeof(packed) isn't as strong as we'd hoped. This makes sure
that when we initialize the padding, all 12 bytes will be zero.

Repository

rCRT Compiler Runtime

Build Status

Buildable 14390
Build 14390: arc lint + arc unit

LGTM

This revision is now accepted and ready to land.Jan 27 2018, 3:21 PM

sync

This revision was automatically updated to reflect the committed changes.

Path

Size

include/

xray/

2 lines

Show First 20 Lines • Show All 90 Lines • ▼ Show 20 Lines	struct alignas(32) XRayRecord {

// Get the full 8 bytes of the TSC when we get the log record.		// Get the full 8 bytes of the TSC when we get the log record.
uint64_t TSC = 0;		uint64_t TSC = 0;

// The thread ID for the currently running thread.		// The thread ID for the currently running thread.
uint32_t TId = 0;		uint32_t TId = 0;

// Use some bytes in the end of the record for buffers.		// Use some bytes in the end of the record for buffers.
char Buffer[4] = {};		char Buffer[12] = {};
} __attribute__((packed));		} __attribute__((packed));

static_assert(sizeof(XRayRecord) == 32, "XRayRecord != 32 bytes");		static_assert(sizeof(XRayRecord) == 32, "XRayRecord != 32 bytes");

struct alignas(32) XRayArgPayload {		struct alignas(32) XRayArgPayload {
// We use the same 16 bits as a discriminant for the records in the log here		// We use the same 16 bits as a discriminant for the records in the log here
// too, and so that the first 4 bytes are packed properly.		// too, and so that the first 4 bytes are packed properly.
uint16_t RecordType = RecordTypes::ARG_PAYLOAD;		uint16_t RecordType = RecordTypes::ARG_PAYLOAD;
Show All 25 Lines