Global: adds a simple tracer

CMakeLists.txt

@@ -105,6 +105,7 @@ cmake_dependent_option(ENABLE_THREADS "Enable multithreading" ON "Threads_FOUND"
 option(ENABLE_ZLIB "Enable zlib" ON)
 option(ENABLE_SYSTEM_YYJSON "Use system provided (instead of fastfetch embedded) yyjson library" OFF)
 option(ENABLE_ASAN "Build fastfetch with ASAN (address sanitizer)" OFF)
+option(ENABLE_TRACER "Build fastfetch with function tracing" OFF)
 option(ENABLE_LTO "Enable link-time optimization in release mode if supported" ON)
 option(BUILD_FLASHFETCH "Build flashfetch" ON) # Also build the flashfetch binary
 option(BUILD_TESTS "Build tests" OFF) # Also create test executables
@@ -1365,6 +1366,22 @@ elseif(GNU)
    )
 endif()
 
+if(ENABLE_TRACER)
+    message(STATUS "Tracer is enabled")
+    list(APPEND LIBFASTFETCH_SRC src/common/impl/tracer.c)
+    if(CMAKE_C_COMPILER_ID MATCHES "Clang" AND NOT CMAKE_BUILD_TYPE STREQUAL "Debug")
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -finstrument-functions-after-inlining")
+    else()
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -finstrument-functions -Dinline=\"__attribute__((no_instrument_function)) inline\"")
+    endif()
+    if(NOT WIN32)
+        set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -rdynamic")
+    elseif(CMAKE_C_COMPILER_ID MATCHES "Clang")
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -gcodeview -fuse-ld=lld")
+        set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--pdb=${CMAKE_BINARY_DIR}/fastfetch.pdb")
+    endif()
+endif()
+
 # Proprietary GPU driver APIs
 if(LINUX OR FreeBSD OR WIN32)
     list(APPEND LIBFASTFETCH_SRC src/detection/gpu/gpu_nvidia.c)
@@ -1889,6 +1906,11 @@ elseif(WIN32)
             PRIVATE "runtimeobject"
         )
     endif()
+    if(ENABLE_TRACER)
+        target_link_libraries(libfastfetch
+            PRIVATE "dbghelp"
+        )
+    endif()
 elseif(FreeBSD)
     target_link_libraries(libfastfetch
         PRIVATE "m"

src/common/impl/tracer.c

@@ -0,0 +1,144 @@
+// DON'T CALL ANY EXTERNAL FUNCTION IN THIS FILE
+
+#include <stdio.h>
+#include <time.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+
+#if !_WIN32
+    #include <dlfcn.h>
+    #include <pthread.h>
+    #include <unistd.h>
+#else
+    #include <windows.h>
+    #include <dbghelp.h>
+#endif
+
+#if _WIN32
+static LARGE_INTEGER freq;
+    #define NtCurrentProcess() ((HANDLE) (-1))
+#endif
+
+static struct trace_event {
+    uint64_t ts;
+    uint64_t tid;
+    void* func;
+} events[4 * 1024 * 1024]; // 4M events, 96 MiB memory usage
+static _Atomic uint32_t event_count;
+
+__attribute__((no_instrument_function, always_inline)) static inline uint64_t get_time_us() {
+#if !_WIN32
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    return (uint64_t) (ts.tv_sec * 1000000 + ts.tv_nsec / 1000);
+#else
+    LARGE_INTEGER now;
+    QueryPerformanceCounter(&now);
+    return (uint64_t) (now.QuadPart * 1000000 / freq.QuadPart);
+#endif
+}
+
+#if _WIN32
+__attribute__((constructor, no_instrument_function)) void trace_init() {
+    QueryPerformanceFrequency(&freq);
+}
+#endif
+
+__attribute__((destructor, no_instrument_function)) void trace_fini() {
+#if _WIN32
+    uint32_t pid = (uint32_t) GetCurrentProcessId();
+#else
+    uint32_t pid = (uint32_t) getpid();
+#endif
+
+    char fileName[64];
+    snprintf(fileName, sizeof(fileName), "trace_%d.json", pid);
+    FILE* trace_file = fopen(fileName, "wb");
+    if (!trace_file) {
+        fprintf(stderr, "Failed to open trace file %s for writing\n", fileName);
+        abort();
+    }
+
+    fputs("[\n", trace_file);
+
+#if _WIN32
+    SymSetOptions(SYMOPT_DEFERRED_LOADS | SYMOPT_UNDNAME);
+    SymInitialize(NtCurrentProcess(), NULL, TRUE);
+#endif
+
+    const char* fnName = NULL;
+
+    uint32_t count = atomic_load_explicit(&event_count, memory_order_acquire);
+    for (uint32_t i = 0; i < count; ++i) {
+        void* fn = events[i].func;
+        uint64_t ts = events[i].ts;
+        bool is_exit = (ts >> 63) != 0;
+        ts &= ~(1ULL << 63); // clear the highest bit
+        uint64_t tid = events[i].tid;
+
+#if _WIN32
+        char buffer[sizeof(SYMBOL_INFO) + MAX_SYM_NAME * sizeof(TCHAR)];
+        PSYMBOL_INFO pSymbol = (PSYMBOL_INFO) buffer;
+        pSymbol->SizeOfStruct = sizeof(SYMBOL_INFO);
+        pSymbol->MaxNameLen = MAX_SYM_NAME;
+
+        DWORD64 displacement = 0;
+        if (SymFromAddr(NtCurrentProcess(), (DWORD64) fn, &displacement, pSymbol)) {
+            fnName = pSymbol->Name;
+        }
+#else
+        char buffer[32];
+        Dl_info info;
+        if (dladdr(fn, &info) && info.dli_sname) {
+            fnName = info.dli_sname;
+        }
+#endif
+
+        else {
+            snprintf(buffer, sizeof(buffer), "%p", fn);
+            fnName = buffer;
+        }
+
+        fprintf(trace_file, "{\"name\":\"%s\",\"ph\":\"%c\",\"pid\":%" PRIu32 ",\"tid\":%" PRIu64 ",\"ts\":%" PRIu64 "}%c\n", fnName, is_exit ? 'E' : 'B', pid, tid, ts, i < count - 1 ? ',' : ' ');
+    }
+
+    fputs("\n]\n", trace_file);
+    fclose(trace_file);
+    fprintf(stderr, "Trace written to trace_%d.json with %u events. Use https://ui.perfetto.dev/ to view it.\n", pid, count);
+
+#if _WIN32
+    SymCleanup(NtCurrentProcess());
+#endif
+}
+
+__attribute__((no_instrument_function)) static void write_event(void* this_fn, bool is_exit) {
+    uint32_t idx = atomic_fetch_add_explicit(&event_count, 1, memory_order_relaxed);
+    if (__builtin_expect(idx >= sizeof(events) / sizeof(events[0]), false)) {
+        abort();
+    }
+
+    events[idx].ts = get_time_us();
+#if _WIN32
+    events[idx].tid = (uint64_t) GetCurrentThreadId();
+#else
+    events[idx].tid = (uint64_t) (uintptr_t) pthread_self();
+#endif
+    events[idx].func = this_fn;
+    if (is_exit) {
+        events[idx].ts |= (1ULL << 63); // set the highest bit to indicate function exit
+    }
+}
+
+__attribute__((no_instrument_function)) void __cyg_profile_func_enter(void* this_fn, void* call_site) {
+    (void) call_site;
+    write_event(this_fn, false);
+}
+
+__attribute__((no_instrument_function)) void __cyg_profile_func_exit(void* this_fn, void* call_site) {
+    (void) call_site;
+    write_event(this_fn, true);
+}