include/glib-compat.h

   1 /*
   2  * GLIB Compatibility Functions
   3  *
   4  * Copyright IBM, Corp. 2013
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *  Michael Tokarev   <mjt@tls.msk.ru>
   9  *  Paolo Bonzini     <pbonzini@redhat.com>
  10  *
  11  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  12  * See the COPYING file in the top-level directory.
  13  *
  14  */
  15
  16 #ifndef QEMU_GLIB_COMPAT_H
  17 #define QEMU_GLIB_COMPAT_H
  18
  19 /* Ask for warnings for anything that was marked deprecated in
  20  * the defined version, or before. It is a candidate for rewrite.
  21  */
  22 #define GLIB_VERSION_MIN_REQUIRED GLIB_VERSION_2_56
  23
  24 /* Ask for warnings if code tries to use function that did not
  25  * exist in the defined version. These risk breaking builds
  26  */
  27 #define GLIB_VERSION_MAX_ALLOWED GLIB_VERSION_2_56
  28
  29 #pragma GCC diagnostic push
  30 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
  31
  32 #include <glib.h>
  33 #if defined(G_OS_UNIX)
  34 #include <glib-unix.h>
  35 #include <sys/types.h>
  36 #include <pwd.h>
  37 #endif
  38
  39 /*
  40  * Note that because of the GLIB_VERSION_MAX_ALLOWED constant above, allowing
  41  * use of functions from newer GLib via this compat header needs a little
  42  * trickery to prevent warnings being emitted.
  43  *
  44  * Consider a function from newer glib-X.Y that we want to use
  45  *
  46  *    int g_foo(const char *wibble)
  47  *
  48  * We must define a static inline function with the same signature that does
  49  * what we need, but with a "_compat" suffix e.g.
  50  *
  51  * static inline void g_foo_compat(const char *wibble)
  52  * {
  53  *     #if GLIB_CHECK_VERSION(X, Y, 0)
  54  *        g_foo(wibble)
  55  *     #else
  56  *        g_something_equivalent_in_older_glib(wibble);
  57  *     #endif
  58  * }
  59  *
  60  * The #pragma at the top of this file turns off -Wdeprecated-declarations,
  61  * ensuring this wrapper function impl doesn't trigger the compiler warning
  62  * about using too new glib APIs. Finally we can do
  63  *
  64  *   #define g_foo(a) g_foo_compat(a)
  65  *
  66  * So now the code elsewhere in QEMU, which *does* have the
  67  * -Wdeprecated-declarations warning active, can call g_foo(...) as normal,
  68  * without generating warnings.
  69  */
  70
  71 /*
  72  * g_memdup2_qemu:
  73  * @mem: (nullable): the memory to copy.
  74  * @byte_size: the number of bytes to copy.
  75  *
  76  * Allocates @byte_size bytes of memory, and copies @byte_size bytes into it
  77  * from @mem. If @mem is %NULL it returns %NULL.
  78  *
  79  * This replaces g_memdup(), which was prone to integer overflows when
  80  * converting the argument from a #gsize to a #guint.
  81  *
  82  * This static inline version is a backport of the new public API from
  83  * GLib 2.68, kept internal to GLib for backport to older stable releases.
  84  * See https://gitlab.gnome.org/GNOME/glib/-/issues/2319.
  85  *
  86  * Returns: (nullable): a pointer to the newly-allocated copy of the memory,
  87  *          or %NULL if @mem is %NULL.
  88  */
  89 static inline gpointer g_memdup2_qemu(gconstpointer mem, gsize byte_size)
  90 {
  91 #if GLIB_CHECK_VERSION(2, 68, 0)
  92     return g_memdup2(mem, byte_size);
  93 #else
  94     gpointer new_mem;
  95
  96     if (mem && byte_size != 0) {
  97         new_mem = g_malloc(byte_size);
  98         memcpy(new_mem, mem, byte_size);
  99     } else {
 100         new_mem = NULL;
 101     }
 102
 103     return new_mem;
 104 #endif
 105 }
 106 #define g_memdup2(m, s) g_memdup2_qemu(m, s)
 107
 108 #if defined(G_OS_UNIX)
 109 /*
 110  * Note: The fallback implementation is not MT-safe, and it returns a copy of
 111  * the libc passwd (must be g_free() after use) but not the content. Because of
 112  * these important differences the caller must be aware of, it's not #define for
 113  * GLib API substitution.
 114  */
 115 static inline struct passwd *
 116 g_unix_get_passwd_entry_qemu(const gchar *user_name, GError **error)
 117 {
 118 #if GLIB_CHECK_VERSION(2, 64, 0)
 119     return g_unix_get_passwd_entry(user_name, error);
 120 #else
 121     struct passwd *p = getpwnam(user_name);
 122     if (!p) {
 123         g_set_error_literal(error, G_UNIX_ERROR, 0, g_strerror(errno));
 124         return NULL;
 125     }
 126     return (struct passwd *)g_memdup(p, sizeof(*p));
 127 #endif
 128 }
 129 #endif /* G_OS_UNIX */
 130
 131 static inline bool
 132 qemu_g_test_slow(void)
 133 {
 134     static int cached = -1;
 135     if (cached == -1) {
 136         cached = g_test_slow() || getenv("G_TEST_SLOW") != NULL;
 137     }
 138     return cached;
 139 }
 140
 141 #undef g_test_slow
 142 #undef g_test_thorough
 143 #undef g_test_quick
 144 #define g_test_slow() qemu_g_test_slow()
 145 #define g_test_thorough() qemu_g_test_slow()
 146 #define g_test_quick() (!qemu_g_test_slow())
 147
 148 #pragma GCC diagnostic pop
 149
 150 #endif