qemu/include/glib-compat.h

/*
 * GLIB Compatibility Functions
 *
 * Copyright IBM, Corp. 2013
 *
 * Authors:
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *  Michael Tokarev   <mjt@tls.msk.ru>
 *  Paolo Bonzini     <pbonzini@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#ifndef QEMU_GLIB_COMPAT_H
#define QEMU_GLIB_COMPAT_H

/* Ask for warnings for anything that was marked deprecated in
 * the defined version, or before. It is a candidate for rewrite.
 */
#define GLIB_VERSION_MIN_REQUIRED GLIB_VERSION_2_56

/* Ask for warnings if code tries to use function that did not
 * exist in the defined version. These risk breaking builds
 */
#define GLIB_VERSION_MAX_ALLOWED GLIB_VERSION_2_56

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"

#include <glib.h>
#if defined(G_OS_UNIX)
#include <glib-unix.h>
#include <sys/types.h>
#include <pwd.h>
#endif

/*
 * Note that because of the GLIB_VERSION_MAX_ALLOWED constant above, allowing
 * use of functions from newer GLib via this compat header needs a little
 * trickery to prevent warnings being emitted.
 *
 * Consider a function from newer glib-X.Y that we want to use
 *
 *    int g_foo(const char *wibble)
 *
 * We must define a static inline function with the same signature that does
 * what we need, but with a "_compat" suffix e.g.
 *
 * static inline void g_foo_compat(const char *wibble)
 * {
 *     #if GLIB_CHECK_VERSION(X, Y, 0)
 *        g_foo(wibble)
 *     #else
 *        g_something_equivalent_in_older_glib(wibble);
 *     #endif
 * }
 *
 * The #pragma at the top of this file turns off -Wdeprecated-declarations,
 * ensuring this wrapper function impl doesn't trigger the compiler warning
 * about using too new glib APIs. Finally we can do
 *
 *   #define g_foo(a) g_foo_compat(a)
 *
 * So now the code elsewhere in QEMU, which *does* have the
 * -Wdeprecated-declarations warning active, can call g_foo(...) as normal,
 * without generating warnings.
 */

/*
 * g_memdup2_qemu:
 * @mem: (nullable): the memory to copy.
 * @byte_size: the number of bytes to copy.
 *
 * Allocates @byte_size bytes of memory, and copies @byte_size bytes into it
 * from @mem. If @mem is %NULL it returns %NULL.
 *
 * This replaces g_memdup(), which was prone to integer overflows when
 * converting the argument from a #gsize to a #guint.
 *
 * This static inline version is a backport of the new public API from
 * GLib 2.68, kept internal to GLib for backport to older stable releases.
 * See https://gitlab.gnome.org/GNOME/glib/-/issues/2319.
 *
 * Returns: (nullable): a pointer to the newly-allocated copy of the memory,
 *          or %NULL if @mem is %NULL.
 */
static inline gpointer g_memdup2_qemu(gconstpointer mem, gsize byte_size)
{
#if GLIB_CHECK_VERSION(2, 68, 0)
    return g_memdup2(mem, byte_size);
#else
    gpointer new_mem;

    if (mem && byte_size != 0) {
        new_mem = g_malloc(byte_size);
        memcpy(new_mem, mem, byte_size);
    } else {
        new_mem = NULL;
    }

    return new_mem;
#endif
}
#define g_memdup2(m, s) g_memdup2_qemu(m, s)

#if defined(G_OS_UNIX)
/*
 * Note: The fallback implementation is not MT-safe, and it returns a copy of
 * the libc passwd (must be g_free() after use) but not the content. Because of
 * these important differences the caller must be aware of, it's not #define for
 * GLib API substitution.
 */
static inline struct passwd *
g_unix_get_passwd_entry_qemu(const gchar *user_name, GError **error)
{
#if GLIB_CHECK_VERSION(2, 64, 0)
    return g_unix_get_passwd_entry(user_name, error);
#else
    struct passwd *p = getpwnam(user_name);
    if (!p) {
        g_set_error_literal(error, G_UNIX_ERROR, 0, g_strerror(errno));
        return NULL;
    }
    return (struct passwd *)g_memdup(p, sizeof(*p));
#endif
}
#endif /* G_OS_UNIX */

static inline bool
qemu_g_test_slow(void)
{
    static int cached = -1;
    if (cached == -1) {
        cached = g_test_slow() || getenv("G_TEST_SLOW") != NULL;
    }
    return cached;
}

#undef g_test_slow
#undef g_test_thorough
#undef g_test_quick
#define g_test_slow() qemu_g_test_slow()
#define g_test_thorough() qemu_g_test_slow()
#define g_test_quick() (!qemu_g_test_slow())

#pragma GCC diagnostic pop

#endif