Expose Wemeet Linux version internal logs

printlog.c

// Usage: 
//    gcc ./printlog.c -shared -o libwemeet_log_override.so -fPIC -Wall -Wextra
//    export LD_PRELOAD=$(realpath ./libwemeet_log_override.so)
#include <execinfo.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

typedef struct {
  const char *ptr;
  size_t size;
  size_t capacity;
} fake_std_string;

static int g_printlog_enabled = -1;
static int g_backtrace_depth = -1;

// hijack the base::log::PrintLog() function
void PrintLog(fake_std_string *tag, fake_std_string *file, int line,
              fake_std_string *func, int level,
              fake_std_string
                  *msg) __asm__("_ZN4base3log8PrintLogEONSt7__cxx1112basic_"
                                "stringIcSt11char_traitsIcESaIcEEES7_iS7_iS7_");

void PrintLog(fake_std_string *tag, fake_std_string *file, int line,
              fake_std_string *func, int level, fake_std_string *msg) {
  if (g_printlog_enabled < 0) {
    g_printlog_enabled = getenv("WEMEET_PRINTLOG") ? 1 : 0;
  }
  if (g_printlog_enabled == 0) {
    return;
  }

  printf("PrintLog: "
         "level=`%d`, file=`%.*s:%d`, tag=`%.*s`, func=`%.*s`, "
         "msg=`%.*s`\n",
         level, (int)file->size, file->ptr, line, (int)tag->size, tag->ptr,
         (int)func->size, func->ptr, (int)msg->size, msg->ptr);

  void *frames[32];
  if (g_backtrace_depth < 0) {
    g_backtrace_depth = getenv("WEMEET_PRINTLOG_BACKTRACE_DEPTH")
                            ? atoi(getenv("WEMEET_PRINTLOG_BACKTRACE_DEPTH"))
                            : 0;
    if (g_backtrace_depth > (int)sizeof(frames)) {
      g_backtrace_depth = (int)sizeof(frames);
    }
  }
  if (g_backtrace_depth == 0) {
    return;
  }
  int frame_count = backtrace(frames, g_backtrace_depth);
  char **symbols = backtrace_symbols(frames, frame_count);
  if (symbols != NULL) {
    for (int i = 0; i < frame_count; ++i) {
      printf("\tbt[%d] %s\n", i, symbols[i]);
    }
    free(symbols);
  } else {
    for (int i = 0; i < frame_count; ++i) {
      printf("\tbt[%d] %p\n", i, frames[i]);
    }
  }
  puts("---\n");
}

trace.bt

struct std_string {
    uint64_t ptr;   // char*
    uint64_t size;  // length
    uint64_t cap;   // capacity (top bit = SSO flag)
}

BEGIN
{
  printf("Tracing owl backend selection via symbols (no ucontext)…\n");
}

/* zlog flush (you already confirmed this address is valid in both builds) */
uprobe:/usr/lib/wemeet/libwemeet_base.so:0x8D0870
{
  $p = arg1; if ($p == 0) { exit(); }

  $head = *(uint64)($p + 32);
  $event_id = *(int32)($p + 44);
  $ctx_dp = *(uint64)($p + 56);
  $name_dp = *(uint64)($p + 88);
  $src_dp = *(uint64)($p + 120);
  $pay_dp = *(uint64)($p + 152);
  $rc = *(int32)($p + 184);
  $tls = *(uint64)($p + 208);

  printf("--- zlog --- \nid=%d rc=%d tls=%p head='%s' name='%s' src='%s' payload='%s' ctx='%s'\n stack=%s\n",
		$event_id, $rc, $tls, str($head), str($name_dp), str($src_dp), str($pay_dp), str($ctx_dp), ustack(perf));
}

/* Coroutine trampoline (present as a symbol across builds). If this never fires, coroutines aren’t used. */
uprobe:/usr/lib/wemeet/libwemeet_base.so:co_jump_to_link
{
  printf("co_jump_to_link(link=%p)\n", arg1);
}

/* Coroutine trampoline (present as a symbol across builds). If this never fires, coroutines aren’t used. */
uprobe:/usr/lib/wemeet/libwemeet_base.so:"*PrintLog*"
{
    $tag   = *(struct std_string *)arg0;
    $file  = *(struct std_string *)arg1;
    $func  = *(struct std_string *)arg3;
    $msg   = *(struct std_string *)arg5;

    printf("PrintLog:  tag=\"%s\"  file=\"%s\"  line=%d  func=\"%s\"  level=%d\n  msg=\"%s\"",
        str($tag.ptr,  $tag.size),
        str($file.ptr, $file.size),
        arg2,
        str($func.ptr, $func.size),
        arg4,
        str($msg.ptr,  $msg.size));
}