ir: Handle overflowing integer constant evaluation properly.

Fixes #1380

Author: emilio

src/clang.rs

@@ -12,7 +12,7 @@ use std::ffi::{CStr, CString};
 use std::fmt;
 use std::hash::Hash;
 use std::hash::Hasher;
-use std::os::raw::{c_char, c_int, c_uint, c_ulong};
+use std::os::raw::{c_char, c_int, c_uint, c_ulong, c_longlong, c_ulonglong};
 
 /// A cursor into the Clang AST, pointing to an AST node.
 ///
@@ -1786,13 +1786,34 @@ impl EvalResult {
     }
 
     /// Try to get back the result as an integer.
-    pub fn as_int(&self) -> Option<i32> {
-        match self.kind() {
-            CXEval_Int => {
-                Some(unsafe { clang_EvalResult_getAsInt(self.x) } as i32)
+    pub fn as_int(&self) -> Option<i64> {
+        if self.kind() != CXEval_Int {
+            return None;
+        }
+
+        if !clang_EvalResult_isUnsignedInt::is_loaded() {
+            // FIXME(emilio): There's no way to detect underflow here, and clang
+            // will just happily give us a value.
+            return Some(unsafe { clang_EvalResult_getAsInt(self.x) } as i64)
+        }
+
+        if unsafe { clang_EvalResult_isUnsignedInt(self.x) } != 0 {
+            let value = unsafe { clang_EvalResult_getAsUnsigned(self.x) };
+            if value > i64::max_value() as c_ulonglong {
+                return None;
             }
-            _ => None,
+
+            return Some(value as i64)
+        }
+
+        let value = unsafe { clang_EvalResult_getAsLongLong(self.x) };
+        if value > i64::max_value() as c_longlong {
+            return None;
+        }
+        if value < i64::min_value() as c_longlong {
+            return None;
         }
+        Some(value as i64)
     }
 
     /// Evaluates the expression as a literal string, that may or may not be

src/ir/var.rs

@@ -265,8 +265,7 @@ impl ClangSubItemParser for Var {
 
                     let mut val = cursor
                         .evaluate()
-                        .and_then(|v| v.as_int())
-                        .map(|val| val as i64);
+                        .and_then(|v| v.as_int());
                     if val.is_none() || !kind.signedness_matches(val.unwrap()) {
                         let tu = ctx.translation_unit();
                         val = get_integer_literal_from_cursor(&cursor, tu);

tests/expectations/tests/error-E0600-cannot-apply-unary-negation-to-u32.rs

@@ -15,6 +15,10 @@ extern "C" {
     #[link_name = "\u{1}k_expr"]
     pub static mut k_expr: EasyToOverflow;
 }
+extern "C" {
+    #[link_name = "\u{1}wow"]
+    pub static mut wow: EasyToOverflow;
+}
 extern "C" {
     #[link_name = "\u{1}BAZ"]
     pub static mut BAZ: ::std::os::raw::c_longlong;

tests/expectations/tests/libclang-3.8/constant-evaluate.rs

@@ -0,0 +1,10 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+pub const a: u32 = 18446744073709551611;

tests/expectations/tests/libclang-3.8/error-E0600-cannot-apply-unary-negation-to-u32.rs

@@ -15,6 +15,10 @@ pub enum _bindgen_ty_1 {
 pub type EasyToOverflow = ::std::os::raw::c_ulonglong;
 pub const k: EasyToOverflow = 2147483648;
 pub const k_expr: EasyToOverflow = 0;
+extern "C" {
+    #[link_name = "\u{1}wow"]
+    pub static mut wow: EasyToOverflow;
+}
 pub const BAZ: ::std::os::raw::c_longlong = 24;
 pub const fuzz: f64 = 51.0;
 pub const BAZZ: ::std::os::raw::c_char = 53;

tests/expectations/tests/libclang-3.9/constant-evaluate.rs

@@ -0,0 +1,10 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+pub const a: u32 = 18446744073709551611;

tests/expectations/tests/libclang-3.9/error-E0600-cannot-apply-unary-negation-to-u32.rs

@@ -1,6 +1,11 @@
 /* automatically generated by rust-bindgen */
 
-#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
 
 pub const foo: _bindgen_ty_1 = _bindgen_ty_1::foo;
 pub const bar: _bindgen_ty_1 = _bindgen_ty_1::bar;
@@ -12,7 +17,8 @@ pub enum _bindgen_ty_1 {
 }
 pub type EasyToOverflow = ::std::os::raw::c_ulonglong;
 pub const k: EasyToOverflow = 2147483648;
-pub const k_expr: EasyToOverflow = 0;
+pub const k_expr: EasyToOverflow = 1152921504606846976;
+pub const wow: EasyToOverflow = 2147483648;
 pub const BAZ: ::std::os::raw::c_longlong = 24;
 pub const fuzz: f64 = 51.0;
 pub const BAZZ: ::std::os::raw::c_char = 53;

tests/expectations/tests/libclang-4/constant-evaluate.rs

@@ -0,0 +1,10 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+pub const a: u32 = 4294967291;

tests/expectations/tests/libclang-4/error-E0600-cannot-apply-unary-negation-to-u32.rs

@@ -1,6 +1,11 @@
 /* automatically generated by rust-bindgen */
 
-#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
 
 pub const foo: _bindgen_ty_1 = _bindgen_ty_1::foo;
 pub const bar: _bindgen_ty_1 = _bindgen_ty_1::bar;
@@ -12,7 +17,8 @@ pub enum _bindgen_ty_1 {
 }
 pub type EasyToOverflow = ::std::os::raw::c_ulonglong;
 pub const k: EasyToOverflow = 2147483648;
-pub const k_expr: EasyToOverflow = 0;
+pub const k_expr: EasyToOverflow = 1152921504606846976;
+pub const wow: EasyToOverflow = 2147483648;
 pub const BAZ: ::std::os::raw::c_longlong = 24;
 pub const fuzz: f64 = 51.0;
 pub const BAZZ: ::std::os::raw::c_char = 53;