text: /*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
  │vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
  ╞══════════════════════════════════════════════════════════════════════════════╡
  │ Copyright 2020 Justine Alexandra Roberts Tunney                              │
  │                                                                              │
  │ Permission to use, copy, modify, and/or distribute this software for         │
  │ any purpose with or without fee is hereby granted, provided that the         │
  │ above copyright notice and this permission notice appear in all copies.      │
  │                                                                              │
  │ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
  │ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
  │ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
  │ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
  │ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
  │ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
  │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
  │ PERFORMANCE OF THIS SOFTWARE.                                                │
  ╚─────────────────────────────────────────────────────────────────────────────*/
  #include "libc/bits/safemacros.h"
  #include "libc/calls/calls.h"
  #include "libc/fmt/fmt.h"
  #include "libc/log/gdb.h"
  #include "libc/log/log.h"
  #include "libc/nexgen32e/stackframe.h"
  #include "libc/runtime/runtime.h"
  #include "libc/runtime/symbols.internal.h"
  
  /**
   * Attachs GDB temporarilly, to do something like print a variable.
   */
  int(gdbexec)(const char *cmd) {
    struct StackFrame *bp;
    int pid, ttyin, ttyout;
    intptr_t continuetoaddr;
    const char *se, *elf, *gdb;
    char pidstr[11], breakcmd[40];
    if (!(gdb = GetGdbPath())) return -1;
    snprintf(pidstr, sizeof(pidstr), "%u", getpid());
    if ((elf = FindDebugBinary())) {
      se = "-se";
    } else {
      se = "-q";
      elf = "-q";
    }
    bp = __builtin_frame_address(0);
    continuetoaddr = bp->addr;
    sprintf(breakcmd, "%s *%#p", "break", bp->addr);
    if (!(pid = vfork())) {
      execv(gdb, (char *const[]){
                     "gdb",
                     "--nx",
                     "--nh",
                     "-p",
                     pidstr,
                     se,
                     elf,
                     "-ex",
                     "set osabi GNU/Linux",
                     "-ex",
                     "set complaints 0",
                     "-ex",
                     "set confirm off",
                     "-ex",
                     "set var g_gdbsync = 1",
                     "-q",
                     "-ex",
                     breakcmd,
                     "-ex",
                     cmd,
                     "-ex",
                     "quit",
                     NULL,
                 });
      abort();
    }
    return SYNCHRONIZE_DEBUGGER(pid);
  }
  