trace.h

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/* -*- C -*-
 * Serene programming language
 * Copyright (C) 2019-2026 Sameer Rahmani <[email protected]>
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#pragma once
/** @file
 Platform neutral static tracepoints.
 
 SRN_TP(group, name, args...) is a probe a tracer observes only when
 attached. It maps to the native facility per platform and falls back to a no-op
 that still marks its arguments used on platforms with no facility, such as
 WebAssembly. Call sites never name a platform; this header owns that choice.
*/
 
// Keep the arguments in an unevaluated context. Nothing is evaluated, no side
// effect runs, but each argument counts as used, so -Werror -Wunused is happy.
#define SRN_TP_CONSUME(...)
//((void)sizeof((0 __VA_OPT__(, ) __VA_ARGS__)))
 
/**
 * Placement matters. SRN_TRACEPOINT expands to a probe instruction the compiler
 * may leave right at a function's epilogue. Never put it as the last statement
 * before a fiber's `return`. A fiber entry returns into the context switch
 * trampoline, and a tracer breakpoint sitting on that teardown trips the stack
 * protector and aborts the process under perf. Put it on an ordinary reachable
 * statement with real code after it, and never right after a loop that never
 * exits, where the optimizer deletes the probe. To mark a fiber's own start and
 * end, emit from the scheduler around the switch rather than from inside the
 * fiber.
 */
#if defined(__linux__)
#  include "../../vendor/usdt.h"
#  define SRN_TRACEPOINT(name, ...) USDT(serene, name __VA_OPT__(, ) __VA_ARGS__)
#  define SRN_TRACEPOINT_WITH_GROUP(group, name, ...) \
    USDT(serene_##group, name __VA_OPT__(, ) __VA_ARGS__)
 
#elif defined(__APPLE__)
#  include <os/signpost.h>
#  define SRN_TRACEPOINT(name, ...)                                                      \
    do {                                                                                 \
      os_signpost_event_emit(OS_LOG_DEFAULT, OS_SIGNPOST_ID_EXCLUSIVE, "serene." #name); \
      SRN_TP_CONSUME(__VA_ARGS__);                                                       \
    } while (0)
#  define SRN_TRACEPOINT_WITH_GROUP(group, name, ...)                                           \
    do {                                                                                        \
      os_signpost_event_emit(OS_LOG_DEFAULT, OS_SIGNPOST_ID_EXCLUSIVE, "serene." #group #name); \
      SRN_TP_CONSUME(__VA_ARGS__);                                                              \
    } while (0)
 
#elif defined(_WIN32)
#  include <TraceLoggingProvider.h>
#  include <windows.h>
TRACELOGGING_DECLARE_PROVIDER(srn_trace_provider);
#  define SRN_TRACEPOINT(name, ...)                                                        \
    do {                                                                                   \
      TraceLoggingWrite(srn_trace_provider, #name, TraceLoggingString("serene", "group")); \
      SRN_TP_CONSUME(__VA_ARGS__);                                                         \
    } while (0)
#  define SRN_TRACEPOINT_WITH_GROUP(group, name, ...)                                              \
    do {                                                                                           \
      TraceLoggingWrite(srn_trace_provider, #name, TraceLoggingString("serene_" #group, "group")); \
      SRN_TP_CONSUME(__VA_ARGS__);                                                                 \
    } while (0)
#else // WebAssembly and any platform with no tracing facility
#  define SRN_TRACEPOINT(name, ...)                   SRN_TP_CONSUME(__VA_ARGS__)
#  define SRN_TRACEPOINT_WITH_GROUP(group, name, ...) SRN_TP_CONSUME(__VA_ARGS__)
#endif