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gatomic: Add a C++ variant of g_atomic_int_compare_and_exchange()

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The C++ variant implements type safety differently, to avoid warnings
from C++ compilers about:
```
../../../gnome-commander-1.14.2/src/intviewer/searcher.cc:303:5: error: cannot initialize a parameter of type 'gint *' (aka 'int *') with an rvalue of type 'void *'
    g_atomic_int_compare_and_exchange ((gint*)&src->priv->progress_value, oldval, (gint)d);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/mnt/b/yoe/master/build/tmp/work/cortexa72-yoe-linux/gnome-commander/1.14.2-r0/recipe-sysroot/usr/include/glib-2.0/glib/gatomic.h:160:44: note: expanded from macro 'g_atomic_int_compare_and_exchange'
    __atomic_compare_exchange_n ((atomic), (void *) (&(gaicae_oldval)), (newval), FALSE, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ? TRUE : FALSE; \
                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~
```

This complements the existing C++ variant for
`g_atomic_pointer_compare_and_exchange()`, and fixes a regression on C++
from https://gitlab.gnome.org/GNOME/glib/-/merge_requests/2114.

With the addition of the unit tests in the previous commit, this is
effectively tested by the FreeBSD and macOS CI jobs, as they use
`clang++` in C++ mode. `g++` doesn’t seem to emit a warning about this.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Fixes: #2625
This commit is contained in:
Philip Withnall 2022-04-01 13:47:19 +01:00
parent 16d1bc49cc
commit ad23894c15
1 changed files with 12 additions and 0 deletions
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12
glib/gatomic.h
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@ -152,6 +152,17 @@ G_END_DECLS
(void) (0 ? *(atomic) ^ *(atomic) : 1); \
__atomic_fetch_sub ((atomic), 1, __ATOMIC_SEQ_CST) == 1; \
}))
#if defined(glib_typeof) && defined(__cplusplus) && __cplusplus >= 201103L
/* See comments below about equivalent g_atomic_pointer_compare_and_exchange()
* shenanigans for type-safety when compiling in C++ mode. */
#define g_atomic_int_compare_and_exchange(atomic, oldval, newval) \
(G_GNUC_EXTENSION ({ \
glib_typeof (*(atomic)) gaicae_oldval = (oldval); \
G_STATIC_ASSERT (sizeof *(atomic) == sizeof (gint)); \
(void) (0 ? *(atomic) ^ (newval) ^ (oldval) : 1); \
__atomic_compare_exchange_n ((atomic), &gaicae_oldval, (newval), FALSE, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ? TRUE : FALSE; \
}))
#else /* if !(defined(glib_typeof) && defined(__cplusplus) && __cplusplus >= 201103L) */
#define g_atomic_int_compare_and_exchange(atomic, oldval, newval) \
(G_GNUC_EXTENSION ({ \
gint gaicae_oldval = (oldval); \
@ -159,6 +170,7 @@ G_END_DECLS
(void) (0 ? *(atomic) ^ (newval) ^ (oldval) : 1); \
__atomic_compare_exchange_n ((atomic), (void *) (&(gaicae_oldval)), (newval), FALSE, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ? TRUE : FALSE; \
}))
#endif /* defined(glib_typeof) */
#define g_atomic_int_add(atomic, val) \
(G_GNUC_EXTENSION ({ \
G_STATIC_ASSERT (sizeof *(atomic) == sizeof (gint)); \