path: root/epan/except.c

/*
 * Portable Exception Handling for ANSI C.
 * Copyright (C) 1999 Kaz Kylheku <kaz@ashi.footprints.net>
 *
 * Free Software License:
 *
 * All rights are reserved by the author, with the following exceptions:
 * Permission is granted to freely reproduce and distribute this software,
 * possibly in exchange for a fee, provided that this copyright notice appears
 * intact. Permission is also granted to adapt this software to produce
 * derivative works, as long as the modified versions carry this copyright
 * notice and additional notices stating that the work has been modified.
 * This source code may be translated into executable form and incorporated
 * into proprietary software; there is no requirement for such software to
 * contain a copyright notice related to this source.
 */

/*
 * Modified to support throwing an exception with a null message pointer,
 * and to have the message not be const (as we generate messages with
 * "ws_strdup_printf()", which means they need to be freed; using
 * a null message means that we don't have to use a special string
 * for exceptions with no message, and don't have to worry about
 * not freeing that).
 */

#include "config.h"

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <limits.h>

#include <glib.h>

#include "except.h"

#ifdef _WIN32
#include <windows.h>
#include "exceptions.h"
#endif

#define XCEPT_BUFFER_SIZE 1024

#ifdef KAZLIB_POSIX_THREADS

#include <pthread.h>

static pthread_mutex_t init_mtx = PTHREAD_MUTEX_INITIALIZER;
static int init_counter;
static pthread_key_t top_key;
static pthread_key_t uh_key;
static pthread_key_t alloc_key;
static pthread_key_t dealloc_key;
static void unhandled_catcher(except_t *);

#define get_top() ((struct except_stacknode *) pthread_getspecific(top_key))
#define set_top(T) (pthread_setspecific(top_key, (T)), (void)((T) == (struct except_stacknode *) 0))
#define set_catcher(C) (pthread_setspecific(uh_key, (void *) (C)), (void)((C) == (void (*)(except_t *)) 0))
#define set_alloc(A) (pthread_setspecific(alloc_key, (void *) (A)), (void)((A) == (void *(*)(size_t)) 0))
#define set_dealloc(D) (pthread_setspecific(dealloc_key, (void *) (D)), (void)((D) == (void (*)(void *)) 0))

static void (*get_catcher(void))(except_t *)
{
    void (*catcher)(except_t *) = (void (*)(except_t *)) pthread_getspecific(uh_key);
    return (catcher == 0) ? unhandled_catcher : catcher;
}

static void *(*get_alloc(void))(size_t)
{
    void *(*alloc)(size_t) = (void *(*)(size_t)) pthread_getspecific(alloc_key);
    return (alloc == 0) ? malloc : alloc;
}

static void (*get_dealloc(void))(void *)
{
    void (*dealloc)(void *) = (void (*)(void *)) pthread_getspecific(dealloc_key);
    return (dealloc == 0) ? free : dealloc;
}

int except_init(void)
{
    int retval = 1;

    pthread_mutex_lock(&init_mtx);

    assert (init_counter < INT_MAX);

    if (init_counter++ == 0) {
        int top_ok = (pthread_key_create(&top_key, 0) == 0);
        int uh_ok = (pthread_key_create(&uh_key, 0) == 0);
        int alloc_ok = (pthread_key_create(&alloc_key, 0) == 0);
        int dealloc_ok = (pthread_key_create(&dealloc_key, 0) == 0);

        if (!top_ok || !uh_ok || !alloc_ok || !dealloc_ok) {
            retval = 0;
            init_counter = 0;
            if (top_ok)
                pthread_key_delete(top_key);
            if (uh_ok)
                pthread_key_delete(uh_key);
            if (alloc_ok)
                pthread_key_delete(alloc_key);
            if (dealloc_ok)
                pthread_key_delete(dealloc_key);
        }
    }

    pthread_mutex_unlock(&init_mtx);

    return retval;
}

void except_deinit(void)
{
    pthread_mutex_lock(&init_mtx);

    assert (init_counter > 0);

    if (--init_counter == 0) {
        pthread_key_delete(top_key);
        pthread_key_delete(uh_key);
        pthread_key_delete(alloc_key);
        pthread_key_delete(dealloc_key);
    }

    pthread_mutex_unlock(&init_mtx);
}

#else /* not using POSIX thread support */

/*
 * We make the catcher stack per-thread, because we must.
 *
 * We don't make the unhandled-exception-catcher, the allocator, or the
 * deallocator thread-specific, as we don't need to.
 *
 * We don't protext the init level with a mutex, as we only initialize
 * it and de-initialize it once.
 */
static int init_counter;
static void unhandled_catcher(except_t *);
static void (*uh_catcher_ptr)(except_t *) = unhandled_catcher;
/* We need this 'size_t' cast due to a glitch in GLib where g_malloc was prototyped
 * as 'gpointer g_malloc (gulong n_bytes)'. This was later fixed to the correct prototype
 * 'gpointer g_malloc (gsize n_bytes)'. In Wireshark we use the latter prototype
 * throughout the code. We can get away with this even with older versions of GLib by
 * adding a '(void *(*)(size_t))' cast whenever we refer to g_malloc. The only platform
 * supported by Wireshark where this isn't safe (sizeof size_t != sizeof gulong) is Win64.
 * However, we _always_ bundle the newest version of GLib on this platform so
 * the size_t issue doesn't exists here. Pheew.. */
static void *(*allocator)(size_t) = (void *(*)(size_t)) g_malloc;
static void (*deallocator)(void *) = g_free;
static WS_THREAD_LOCAL struct except_stacknode *stack_top;

#define get_top() (stack_top)
#define set_top(T) (stack_top = (T))
#define get_catcher() (uh_catcher_ptr)
#define set_catcher(C) (uh_catcher_ptr = (C))
#define get_alloc() (allocator)
#define set_alloc(A) (allocator = (A))
#define get_dealloc() (deallocator)
#define set_dealloc(D) (deallocator = (D))

int except_init(void)
{
    assert (init_counter < INT_MAX);
    init_counter++;
    return 1;
}

void except_deinit(void)
{
    assert (init_counter > 0);
    init_counter--;
}

#endif


static int match(const volatile except_id_t *thrown, const except_id_t *caught)
{
    int group_match = (caught->except_group == XCEPT_GROUP_ANY ||
        caught->except_group == thrown->except_group);
    int code_match = (caught->except_code == XCEPT_CODE_ANY ||
        caught->except_code == thrown->except_code);

    return group_match && code_match;
}

WS_NORETURN static void do_throw(except_t *except)
{
    struct except_stacknode *top;

    assert (except->except_id.except_group != 0 &&
        except->except_id.except_code != 0);

    for (top = get_top(); top != 0; top = top->except_down) {
        if (top->except_type == XCEPT_CLEANUP) {
            top->except_info.except_cleanup->except_func(top->except_info.except_cleanup->except_context);
        } else {
            struct except_catch *catcher = top->except_info.except_catcher;
            const except_id_t *pi = catcher->except_id;
            size_t i;

            assert (top->except_type == XCEPT_CATCHER);
            except_free(catcher->except_obj.except_dyndata);

            for (i = 0; i < catcher->except_size; pi++, i++) {
                if (match(&except->except_id, pi)) {
                    catcher->except_obj = *except;
                    set_top(top);
                    longjmp(catcher->except_jmp, 1);
                }
            }
        }
    }

    set_top(top);
    get_catcher()(except); /* unhandled exception */
    abort();
}

static void unhandled_catcher(except_t *except)
{
    if (except->except_message == NULL) {
        fprintf(stderr, "Unhandled exception (group=%lu, code=%lu)\n",
                except->except_id.except_group,
                except->except_id.except_code);
    } else {
        fprintf(stderr, "Unhandled exception (\"%s\", group=%lu, code=%lu)\n",
                except->except_message, except->except_id.except_group,
                except->except_id.except_code);
    }
    abort();
}

static void stack_push(struct except_stacknode *node)
{
    node->except_down = get_top();
    set_top(node);
}

void except_setup_clean(struct except_stacknode *esn,
        struct except_cleanup *ecl, void (*cleanf)(void *), void *context)
{
    esn->except_type = XCEPT_CLEANUP;
    ecl->except_func = cleanf;
    ecl->except_context = context;
    esn->except_info.except_cleanup = ecl;
    stack_push(esn);
}

void except_setup_try(struct except_stacknode *esn,
        struct except_catch *ech, const except_id_t id[], size_t size)
{
   ech->except_id = id;
   ech->except_size = size;
   ech->except_obj.except_dyndata = 0;
   esn->except_type = XCEPT_CATCHER;
   esn->except_info.except_catcher = ech;
   stack_push(esn);
}

struct except_stacknode *except_pop(void)
{
    struct except_stacknode *top = get_top();
    assert (top->except_type == XCEPT_CLEANUP || top->except_type == XCEPT_CATCHER);
    set_top(top->except_down);
    return top;
}

WS_NORETURN void except_rethrow(except_t *except)
{
    struct except_stacknode *top = get_top();
    assert (top != 0);
    assert (top->except_type == XCEPT_CATCHER);
    assert (&top->except_info.except_catcher->except_obj == except);
    set_top(top->except_down);
    do_throw(except);
}

WS_NORETURN void except_throw(long group, long code, const char *msg)
{
    except_t except;

    except.except_id.except_group = group;
    except.except_id.except_code = code;
    except.except_message = msg;
    except.except_dyndata = 0;

#ifdef _WIN32
    if (code == DissectorError && IsDebuggerPresent()) {
        DebugBreak();
    }
#endif

    do_throw(&except);
}

WS_NORETURN void except_throwd(long group, long code, const char *msg, void *data)
{
    except_t except;

    except.except_id.except_group = group;
    except.except_id.except_code = code;
    except.except_message = msg;
    except.except_dyndata = data;

    do_throw(&except);
}

/*
 * XXX - should we use ws_strdup_printf() here, so we're not limited by
 * XCEPT_BUFFER_SIZE?  We could then just use this to generate formatted
 * messages.
 */
WS_NORETURN void except_vthrowf(long group, long code, const char *fmt,
                                va_list vl)
{
    char *buf = (char *)except_alloc(XCEPT_BUFFER_SIZE);

    vsnprintf(buf, XCEPT_BUFFER_SIZE, fmt, vl);
    except_throwd(group, code, buf, buf);
}

WS_NORETURN void except_throwf(long group, long code, const char *fmt, ...)
{
    va_list vl;

    va_start (vl, fmt);
    except_vthrowf(group, code, fmt, vl);
    va_end (vl);
}

void (*except_unhandled_catcher(void (*new_catcher)(except_t *)))(except_t *)
{
    void (*old_catcher)(except_t *) = get_catcher();
    set_catcher(new_catcher);
    return old_catcher;
}

#undef except_code
#undef except_group
#undef except_message
#undef except_data

unsigned long except_code(except_t *ex)
{
    return ex->except_id.except_code;
}

unsigned long except_group(except_t *ex)
{
    return ex->except_id.except_group;
}

const char *except_message(except_t *ex)
{
    return ex->except_message;
}

void *except_data(except_t *ex)
{
    return ex->except_dyndata;
}

void *except_take_data(except_t *ex)
{
    void *data = ex->except_dyndata;
    ex->except_dyndata = 0;
    return data;
}

void except_set_allocator(void *(*alloc)(size_t), void (*dealloc)(void *))
{
    set_alloc(alloc);
    set_dealloc(dealloc);
}

void *except_alloc(size_t size)
{
    void *ptr = get_alloc()(size);

    if (ptr == 0)
        except_throw(XCEPT_BAD_ALLOC, 0, "out of memory");
    return ptr;
}

void except_free(void *ptr)
{
    get_dealloc()(ptr);
}

#ifdef KAZLIB_TEST_MAIN


static void cleanup(void *arg)
{
    printf("cleanup(\"%s\") called\n", (char *) arg);
}

static void bottom_level(void)
{
    char buf[256];
    printf("throw exception? "); fflush(stdout);
    fgets(buf, sizeof buf, stdin);

    if (buf[0] >= 0 && (buf[0] == 'Y' || buf[0] == 'y'))
        except_throw(1, 1, "nasty exception");
}

static void top_level(void)
{
    except_cleanup_push(cleanup, "argument");
    bottom_level();
    except_cleanup_pop(0);
}

int main(int argc, char **argv)
{
    static const except_id_t catch[] = { { 1, 1 }, { 1, 2 } };
    except_t *ex;
    char *msg;

    /*
     * Nested exception ``try blocks''
     */

    /* outer */
    except_try_push(catch, 2, &ex);
    if (!ex) {
        /* inner */
        except_try_push(catch, 2, &ex);
        if (!ex) {
            top_level();
        } else {
            /* inner catch */
            msg = except_message(ex);
            if (msg == NULL) {
                printf("caught exception (inner): s=%lu, c=%lu\n",
                       except_group(ex), except_code(ex));
            } else {
                printf("caught exception (inner): \"%s\", s=%lu, c=%lu\n",
                       msg, except_group(ex), except_code(ex));
            }
            except_rethrow(ex);
        }
        except_try_pop();
    } else {
        /* outer catch */
        msg = except_message(ex);
        if (msg == NULL) {
            printf("caught exception (outer): s=%lu, c=%lu\n",
                   except_group(ex), except_code(ex));
        } else {
            printf("caught exception (outer): \"%s\", s=%lu, c=%lu\n",
                   except_message(ex), except_group(ex), except_code(ex));
        }
    }
    except_try_pop();
    except_throw(99, 99, "exception in main");
    return 0;
}


#endif /* KAZLIB_TEST_MAIN */

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 4
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * vi: set shiftwidth=4 tabstop=8 expandtab:
 * :indentSize=4:tabSize=8:noTabs=true:
 */