* First try at libzzuf.

configure.ac

@@ -12,6 +12,7 @@ AM_CONFIG_HEADER(config.h)
 
 AM_PROG_CC_C_O
 AC_PROG_CPP
+AC_PROG_LIBTOOL
 
 dnl AC_PROG_EGREP only exists in autoconf 2.54+, so we use AC_EGREP_CPP right
 dnl now otherwise it might be set in an obscure if statement. Same thing for

src/Makefile.am

@@ -2,3 +2,8 @@
 bin_PROGRAMS = zzuf
 zzuf_SOURCES = zzuf.c random.c
 
+pkglib_LTLIBRARIES = libzzuf.la
+libzzuf_la_SOURCES = libzzuf.c
+libzzuf_la_LDFLAGS = -module
+libzzuf_la_LIBADD = -ldl
+

src/libzzuf.c

@@ -0,0 +1,109 @@
+/*
+ *  zzuf - general purpose fuzzer
+ *  Copyright (c) 2006 Sam Hocevar <sam@zoy.org>
+ *                All Rights Reserved
+ *
+ *  $Id$
+ *
+ *  This program is free software. It comes without any warranty, to
+ *  the extent permitted by applicable law. You can redistribute it
+ *  and/or modify it under the terms of the Do What The Fuck You Want
+ *  To Public License, Version 2, as published by Sam Hocevar. See
+ *  http://sam.zoy.org/wtfpl/COPYING for more details.
+ */
+
+/*
+ *  libzzuf.c: preloaded wrapper library
+ */
+
+#include "config.h"
+#define _GNU_SOURCE
+
+#if defined HAVE_STDINT_H
+#   include <stdint.h>
+#elif defined HAVE_INTTYPES_H
+#   include <inttypes.h>
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+
+#include <stdarg.h>
+#include <dlfcn.h>
+
+static int do_debug = 0;
+static void debug(const char *format, ...)
+{
+    if(!do_debug)
+        return;
+
+    va_list args;
+    va_start(args, format);
+    fprintf(stderr, "** zzuf debug ** ");
+    vfprintf(stderr, format, args);
+    fprintf(stderr, "\n");
+    va_end(args);
+}
+
+/* Library functions that we divert */
+static FILE * (*fopen_orig) (const char *path, const char *mode);
+static int (*open_orig) (const char *file, int oflag, ...);
+static int (*open64_orig) (const char *file, int oflag, ...);
+
+/* Library initialisation shit */
+void zzufinit(void) __attribute__((constructor));
+void zzufinit(void)
+{
+    char *tmp;
+
+    fopen_orig = dlsym(RTLD_NEXT, "fopen");
+    open_orig  = dlsym(RTLD_NEXT, "open");
+    open64_orig  = dlsym(RTLD_NEXT, "open");
+
+    tmp = getenv("ZZUF_DEBUG");
+    if(tmp && *tmp)
+        do_debug = 1;
+}
+
+/* Our function wrappers */
+FILE *fopen(const char *path, const char *mode)
+{
+    debug("fopen(\"%s\", \"%s\");", path, mode);
+    return fopen_orig(path, mode);
+}
+
+#define STR(x) STR2(x)
+#define STR2(x) #x
+#define ORIG(x) ORIG2(x)
+#define ORIG2(x) x##_orig
+#define OPEN(ret, fn, file, oflag) \
+    do { if(oflag & O_CREAT) \
+    { \
+        int mode; \
+        va_list va; \
+        va_start(va, oflag); \
+        mode = va_arg(va, int); \
+        va_end(va); \
+        debug(STR(fn) "(\"%s\", %i, %i);", file, oflag, mode); \
+        ret = ORIG(fn)(file, oflag, mode); \
+    } \
+    else \
+    { \
+        debug(STR(fn) "(\"%s\", %i);", file, oflag); \
+        ret = ORIG(fn)(file, oflag); \
+    } } while(0)
+
+int open(const char *file, int oflag, ...)
+{
+    int ret;
+    OPEN(ret, open, file, oflag);
+    return ret;
+}
+
+int open64(const char *file, int oflag, ...)
+{
+    int ret;
+    OPEN(ret, open64, file, oflag);
+    return ret;
+}
+