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<p>Hi, Sergey</p>
<p><br>
</p>
<p>thanks for the patch! LGTM</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 03.06.2024 17:33, Sergey Kaplun
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:75374f7bfe142c8133f42e96b6a6c55cfe0b7811.1717424008.git.skaplun@tarantool.org">
<pre class="moz-quote-pre" wrap="">From: Mike Pall <mike>
Reported by Eric Gouyer.
(cherry picked from commit 36b2962d400db3981a7d7322f85c469240eb6f3b)
According to C++ Standard (5.3.6.3) [1], the `alignof()` for the
reference should be the same as for the referenced type. This patch
fixes the behaviour by following the reference to get a child id for
`ffi.alignof()`.
Sergey Kaplun:
* added the description and the test for the problem
Part of tarantool/tarantool#9924
[1]: <a class="moz-txt-link-freetext" href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4594.pdf#subsection.5.3.6">https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4594.pdf#subsection.5.3.6</a>
---
src/lib_ffi.c | 2 +-
src/lj_ctype.c | 8 ++++++
src/lj_ctype.h | 1 +
.../lj-861-ctype-attributes.test.lua | 26 +++++++++++++++++++
4 files changed, 36 insertions(+), 1 deletion(-)
create mode 100644 test/tarantool-tests/lj-861-ctype-attributes.test.lua
diff --git a/src/lib_ffi.c b/src/lib_ffi.c
index e60e7b19..2bfca25a 100644
--- a/src/lib_ffi.c
+++ b/src/lib_ffi.c
@@ -639,7 +639,7 @@ LJLIB_CF(ffi_alignof) LJLIB_REC(ffi_xof FF_ffi_alignof)
CTState *cts = ctype_cts(L);
CTypeID id = ffi_checkctype(L, cts, NULL);
CTSize sz = 0;
- CTInfo info = lj_ctype_info(cts, id, &sz);
+ CTInfo info = lj_ctype_info_raw(cts, id, &sz);
setintV(L->top-1, 1 << ctype_align(info));
return 1;
}
diff --git a/src/lj_ctype.c b/src/lj_ctype.c
index 0874fa61..83042118 100644
--- a/src/lj_ctype.c
+++ b/src/lj_ctype.c
@@ -345,6 +345,14 @@ CTInfo lj_ctype_info(CTState *cts, CTypeID id, CTSize *szp)
return qual;
}
+/* Ditto, but follow a reference. */
+CTInfo lj_ctype_info_raw(CTState *cts, CTypeID id, CTSize *szp)
+{
+ CType *ct = ctype_get(cts, id);
+ if (ctype_isref(ct->info)) id = ctype_cid(ct->info);
+ return lj_ctype_info(cts, id, szp);
+}
+
/* Get ctype metamethod. */
cTValue *lj_ctype_meta(CTState *cts, CTypeID id, MMS mm)
{
diff --git a/src/lj_ctype.h b/src/lj_ctype.h
index fce29409..8edbd561 100644
--- a/src/lj_ctype.h
+++ b/src/lj_ctype.h
@@ -467,6 +467,7 @@ LJ_FUNC CType *lj_ctype_rawref(CTState *cts, CTypeID id);
LJ_FUNC CTSize lj_ctype_size(CTState *cts, CTypeID id);
LJ_FUNC CTSize lj_ctype_vlsize(CTState *cts, CType *ct, CTSize nelem);
LJ_FUNC CTInfo lj_ctype_info(CTState *cts, CTypeID id, CTSize *szp);
+LJ_FUNC CTInfo lj_ctype_info_raw(CTState *cts, CTypeID id, CTSize *szp);
LJ_FUNC cTValue *lj_ctype_meta(CTState *cts, CTypeID id, MMS mm);
LJ_FUNC GCstr *lj_ctype_repr(lua_State *L, CTypeID id, GCstr *name);
LJ_FUNC GCstr *lj_ctype_repr_int64(lua_State *L, uint64_t n, int isunsigned);
diff --git a/test/tarantool-tests/lj-861-ctype-attributes.test.lua b/test/tarantool-tests/lj-861-ctype-attributes.test.lua
new file mode 100644
index 00000000..d88045a5
--- /dev/null
+++ b/test/tarantool-tests/lj-861-ctype-attributes.test.lua
@@ -0,0 +1,26 @@
+local tap = require('tap')
+
+-- Test file to demonstrate LuaJIT incorrect behaviour during
+-- parsing and working with ctypes with attributes.
+-- See also: <a class="moz-txt-link-freetext" href="https://github.com/LuaJIT/LuaJIT/issues/861">https://github.com/LuaJIT/LuaJIT/issues/861</a>.
+
+local test = tap.test('lj-861-ctype-attributes')
+local ffi = require('ffi')
+
+test:plan(2)
+
+local EXPECTED_ALIGN = 4
+
+ffi.cdef([[
+struct __attribute__((aligned($))) s_aligned {
+ uint8_t a;
+};
+]], EXPECTED_ALIGN)
+
+local ref_align = ffi.alignof(ffi.typeof('struct s_aligned &'))
+
+test:is(ref_align, EXPECTED_ALIGN, 'the reference alignment is correct')
+test:is(ref_align, ffi.alignof(ffi.typeof('struct s_aligned')),
+ 'the alignment of a reference is the same as for the referenced type')
+
+test:done(true)
</pre>
</blockquote>
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