[unsafe] Records that struct libc types do not derive Default (#151)

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -579,6 +579,14 @@ bool Converter::RecordDerivesDefault(const clang::RecordDecl *decl) {
     if (f->getType()->isArrayType()) {
       return false;
     }
+
+    // Records that contain libc types do not derive Default
+    if (auto record = f->getType()->getAsRecordDecl()) {
+      if (ctx_.getSourceManager().isInSystemHeader(record->getLocation()) &&
+          f->getType().isPODType(ctx_)) {
+        return false;
+      }
+    }
   }
 
   return true;
@@ -3163,7 +3171,8 @@ std::string Converter::GetDefaultAsStringFallback(clang::QualType qual_type) {
   if (auto record = qual_type->getAsRecordDecl()) {
     if (ctx_.getSourceManager().isInSystemHeader(record->getLocation()) &&
         qual_type.isPODType(ctx_)) {
-      return std::format("std::mem::zeroed::<{}>()", ToString(qual_type));
+      return std::format("unsafe {{ std::mem::zeroed::<{}>() }}",
+                         ToString(qual_type));
     }
   }
 

tests/unit/libc_struct_without_default.cpp

@@ -3,6 +3,7 @@
 #include <assert.h>
 #include <netinet/in.h>
 #include <poll.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <time.h>
 #include <vector>
@@ -12,6 +13,10 @@ struct UserDefined {
   std::vector<int> v;
 };
 
+struct FieldIsLibcType {
+  struct sockaddr addr;
+};
+
 int main() {
   struct pollfd p;
   p.fd = -1;
@@ -40,5 +45,8 @@ int main() {
   UserDefined ud;
   assert(ud.a[0] == 0);
   assert(ud.v.size() == 0);
+
+  FieldIsLibcType filt;
+  assert(filt.addr.sa_family == 0);
   return 0;
 }

tests/unit/out/unsafe/libc_struct_without_default.rs

@@ -20,34 +20,48 @@ impl Default for UserDefined {
         }
     }
 }
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct FieldIsLibcType {
+    pub addr: sockaddr,
+}
+impl Default for FieldIsLibcType {
+    fn default() -> Self {
+        FieldIsLibcType {
+            addr: unsafe { std::mem::zeroed::<sockaddr>() },
+        }
+    }
+}
 pub fn main() {
     unsafe {
         std::process::exit(main_0() as i32);
     }
 }
 unsafe fn main_0() -> i32 {
-    let mut p: pollfd = std::mem::zeroed::<pollfd>();
+    let mut p: pollfd = unsafe { std::mem::zeroed::<pollfd>() };
     p.fd = -1_i32;
     p.events = 0_i16;
     p.revents = 2_i16;
     assert!(((p.fd) == (-1_i32)));
     assert!(((p.events as i32) == (0)));
     assert!(((p.revents as i32) == (2)));
-    let mut ia: in_addr = std::mem::zeroed::<in_addr>();
+    let mut ia: in_addr = unsafe { std::mem::zeroed::<in_addr>() };
     ia.s_addr = 1_u32;
     assert!(((ia.s_addr) == (1_u32)));
-    let mut t: tm = std::mem::zeroed::<tm>();
+    let mut t: tm = unsafe { std::mem::zeroed::<tm>() };
     t.tm_year = 124;
     t.tm_mon = 5;
     t.tm_mday = 15;
     assert!(((t.tm_year) == (124)));
     assert!(((t.tm_mon) == (5)));
     assert!(((t.tm_mday) == (15)));
-    let mut st: stat = std::mem::zeroed::<stat>();
+    let mut st: stat = unsafe { std::mem::zeroed::<stat>() };
     st.st_size = 1024_i64;
     assert!(((st.st_size) == (1024_i64)));
     let mut ud: UserDefined = <UserDefined>::default();
     assert!(((ud.a[(0_u64) as usize]) == (0)));
     assert!(((ud.v.len() as u64) == (0_u64)));
+    let mut filt: FieldIsLibcType = <FieldIsLibcType>::default();
+    assert!(((filt.addr.sa_family as i32) == (0)));
     return 0;
 }

tests/unit/out/unsafe/socket_transparent_union.rs

@@ -13,7 +13,7 @@ pub fn main() {
 }
 unsafe fn main_0() -> i32 {
     let mut fd: i32 = 0;
-    let mut ssloc: sockaddr_storage = std::mem::zeroed::<sockaddr_storage>();
+    let mut ssloc: sockaddr_storage = unsafe { std::mem::zeroed::<sockaddr_storage>() };
     let mut slen: u32 = (::std::mem::size_of::<sockaddr_storage>() as u64 as u32);
     assert!(
         ((((libc::getsockname(
@@ -23,7 +23,7 @@ unsafe fn main_0() -> i32 {
         )) == (-1_i32)) as i32)
             != 0)
     );
-    let mut sin: sockaddr_in = std::mem::zeroed::<sockaddr_in>();
+    let mut sin: sockaddr_in = unsafe { std::mem::zeroed::<sockaddr_in>() };
     let mut inlen: u32 = (::std::mem::size_of::<sockaddr_in>() as u64 as u32);
     assert!(
         ((((libc::getsockname(

tests/unit/out/unsafe/sys_stat.rs

@@ -18,7 +18,7 @@ pub unsafe fn test_stat_0() {
         fp,
     );
     assert!(((((libc::fclose(fp)) == (0)) as i32) != 0));
-    let mut st: stat = std::mem::zeroed::<stat>();
+    let mut st: stat = unsafe { std::mem::zeroed::<stat>() };
     assert!(((((libc::stat(path as *const i8, (&mut st as *mut stat))) == (0)) as i32) != 0));
     assert!(((((st.st_size) == (5_i64)) as i32) != 0));
     libc::unlink(path as *const i8);
@@ -36,7 +36,7 @@ pub unsafe fn test_fstat_1() {
     );
     libc::fflush(fp);
     let mut fd: i32 = libc::fileno(fp);
-    let mut st: stat = std::mem::zeroed::<stat>();
+    let mut st: stat = unsafe { std::mem::zeroed::<stat>() };
     assert!(((((libc::fstat(fd, (&mut st as *mut stat))) == (0)) as i32) != 0));
     assert!(((((st.st_size) == (11_i64)) as i32) != 0));
     assert!(((((libc::fclose(fp)) == (0)) as i32) != 0));