Allow constant expressions that doesn't fit in i64.

Fixes #2618

Author: zyp

bindgen-tests/tests/expectations/tests/issue-2618.rs

@@ -0,0 +1,18 @@
+// bindgen-flags: --allowlist-var "val[0-9]+"
+
+typedef __UINT32_TYPE__ uint32_t;
+typedef __UINT64_TYPE__ uint64_t;
+
+static const uint32_t val1 = 0x7fffffff;
+static const uint32_t val2 = 0x80000000;
+static const uint32_t val3 = 0xffffffff;
+static const uint64_t val4 = 0x7fffffffffffffff;
+static const uint64_t val5 = 0x8000000000000000;
+static const uint64_t val6 = 0xffffffffffffffff;
+
+static const uint32_t val7 = (0x7fffffff);
+static const uint32_t val8 = (0x80000000);
+static const uint32_t val9 = (0xffffffff);
+static const uint64_t val10 = (0x7fffffffffffffff);
+static const uint64_t val11 = (0x8000000000000000);
+static const uint64_t val12 = (0xffffffffffffffff);

bindgen-tests/tests/headers/issue-2618.h

@@ -2351,10 +2351,11 @@ impl EvalResult {
 
         if unsafe { clang_EvalResult_isUnsignedInt(self.x) } != 0 {
             let value = unsafe { clang_EvalResult_getAsUnsigned(self.x) };
-            if value > i64::MAX as c_ulonglong {
+            if value > u64::MAX as c_ulonglong {
                 return None;
             }
 
+            // Do a wrapping cast to i64. This will be losslessly cast back to u64 later.
             return Some(value as i64);
         }
 

bindgen/clang.rs

@@ -120,9 +120,4 @@ impl IntKind {
             _ => return None,
         })
     }
-
-    /// Whether this type's signedness matches the value.
-    pub(crate) fn signedness_matches(&self, val: i64) -> bool {
-        val >= 0 || self.is_signed()
-    }
 }

bindgen/ir/int.rs

@@ -341,7 +341,7 @@ impl ClangSubItemParser for Var {
                     };
 
                     let mut val = cursor.evaluate().and_then(|v| v.as_int());
-                    if val.is_none() || !kind.signedness_matches(val.unwrap()) {
+                    if val.is_none() {
                         val = get_integer_literal_from_cursor(&cursor);
                     }