ffi: almost bug: 64 bit signed big/little endian type.

* ffi.c (ffi_be_i64_get, ffi_le_i64_get): The code here for 32
bit platforms is fishy: it is using the signed cnum type for
the low 32 bits, when that should be ucnum. We are actually
okay because ths code would only be executed on a platform
where cnum is 32 bits. We are saved by the fact that we are
doing left shifts (no sign extension), that shifting a 1 into
a sign bit is harmless on two's complement machines, and that
the lo32 value is ultimately passed to unum whereby it is
coerced to a ucnum argument type (which preserves the bit
representation) and prevents logior from seeing a negative
value.

1 files changed, 4 insertions, 4 deletions

diff --git a/ffi.c b/ffi.c
index 17936396..672d5749 100644
--- a/ffi.c
+++ b/ffi.c
@@ -975,8 +975,8 @@ static val ffi_be_i64_get(struct txr_ffi_type *tft, mem_t *src, val self)
 #else
   cnum hi32 = (convert(cnum, src[0]) << 24 | convert(cnum, src[1]) << 16 |
                convert(cnum, src[2]) << 8 | src[3]);
-  cnum lo32 = (convert(cnum, src[4]) << 24 | convert(cnum, src[5]) << 16 |
-               convert(cnum, src[6]) << 8 | src[7]);
+  ucnum lo32 = (convert(ucnum, src[4]) << 24 | convert(ucnum, src[5]) << 16 |
+                convert(ucnum, src[6]) << 8 | src[7]);
   return logior(ash(num(hi32), num_fast(32)), unum(lo32));
 #endif
 }
@@ -1089,8 +1089,8 @@ static val ffi_le_i64_get(struct txr_ffi_type *tft, mem_t *src, val self)
 #else
   cnum hi32 = (convert(cnum, src[3]) << 24 | convert(cnum, src[2]) << 16 |
                convert(cnum, src[1]) << 8 | src[0]);
-  cnum lo32 = (convert(cnum, src[3]) << 24 | convert(cnum, src[2]) << 16 |
-               convert(cnum, src[1]) << 8 | src[0]);
+  ucnum lo32 = (convert(ucnum, src[3]) << 24 | convert(ucnum, src[2]) << 16 |
+                convert(ucnum, src[1]) << 8 | src[0]);
   return logior(ash(num(hi32), num_fast(32)), unum(lo32));
 #endif
 }