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[glibc.git] / debug / pcprofile.c
blobeb95856c2db306d581488385f2f0ad1cc1c67920
1 /* Profile PC and write result to FIFO.
2 Copyright (C) 1999, 2000 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1999.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Library General Public License as
8 published by the Free Software Foundation; either version 2 of the
9 License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Library General Public License for more details.
16 You should have received a copy of the GNU Library General Public
17 License along with the GNU C Library; see the file COPYING.LIB. If not,
18 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 #include <errno.h>
22 #include <fcntl.h>
23 #include <stdint.h>
24 #include <stdlib.h>
25 #include <unistd.h>
26 #include <libc-internal.h>
28 /* Nonzero if we are actually doing something. */
29 static int active;
31 /* The file descriptor of the FIFO. */
32 static int fd;
35 static void
36 __attribute__ ((constructor))
37 install (void)
39 /* See whether the environment variable `PCPROFILE_OUTPUT' is defined.
40 If yes, it should name a FIFO. We open it and mark ourself as active. */
41 const char *outfile = getenv ("PCPROFILE_OUTPUT");
43 if (outfile != NULL && *outfile != '\0')
45 fd = open (outfile, O_RDWR | O_CREAT, 0666);
47 if (fd != -1)
49 uint32_t word;
51 active = 1;
53 /* Write a magic word which tells the reader about the byte
54 order and the size of the following entries. */
55 word = 0xdeb00000 | sizeof (void *);
56 if (TEMP_FAILURE_RETRY (write (fd, &word, 4)) != 4)
58 /* If even this fails we shouldn't try further. */
59 close (fd);
60 fd = -1;
61 active = 0;
68 static void
69 __attribute__ ((destructor))
70 uninstall (void)
72 if (active)
73 close (fd);
77 void
78 __cyg_profile_func_enter (void *this_fn, void *call_site)
80 void *buf[2];
82 if (! active)
83 return;
85 /* Now write out the current position and that of the caller. We do
86 this now, and don't cache the because we want real-time output. */
87 buf[0] = this_fn;
88 buf[1] = call_site;
90 write (fd, buf, sizeof buf);
92 /* We don't handle entry and exit differently here. */
93 strong_alias (__cyg_profile_func_enter, __cyg_profile_func_exit)