Support va_copy with a member of a struct pointer

c2rust-transpile/src/translator/variadic.rs

@@ -58,6 +58,23 @@ impl<'c> Translation<'c> {
             Some(va_id)
         }
 
+        // struct-based va_list (e.g. x86_64) where va_list is accessed as a member of a struct pointer
+        // supporting this pattern is necessary to transpile [graphviz](https://gitlab.com/graphviz/graphviz/-/blob/5.0.0/lib/sfio/sftable.c#L321)
+        fn match_vastart_struct_pointer_member(
+            ast_context: &TypedAstContext,
+            expr: CExprId,
+        ) -> Option<CDeclId> {
+            match_or! { [ast_context[expr].kind]
+            CExprKind::ImplicitCast(_, me, _, _, _) => me }
+            match_or! { [ast_context[me].kind]
+            CExprKind::Member(_, ie, _, _, _) => ie }
+            match_or! { [ast_context[ie].kind]
+            CExprKind::ImplicitCast(_, e, _, _, _) => e }
+            match_or! { [ast_context[e].kind]
+            CExprKind::DeclRef(_, va_id, _) => va_id }
+            Some(va_id)
+        }
+
         // char pointer-based va_list (e.g. x86)
         fn match_vastart_pointer(ast_context: &TypedAstContext, expr: CExprId) -> Option<CDeclId> {
             match_or! { [ast_context[expr].kind]
@@ -68,6 +85,7 @@ impl<'c> Translation<'c> {
         match_vastart_struct(&self.ast_context, expr)
             .or_else(|| match_vastart_pointer(&self.ast_context, expr))
             .or_else(|| match_vastart_struct_member(&self.ast_context, expr))
+            .or_else(|| match_vastart_struct_pointer_member(&self.ast_context, expr))
     }
 
     pub fn match_vaend(&self, expr: CExprId) -> Option<CDeclId> {

tests/items/src/test_varargs.rs

@@ -2,7 +2,7 @@
 
 use crate::varargs::{
     rust_call_printf, rust_call_vprintf, rust_my_printf, rust_restart_valist, rust_sample_stddev,
-    rust_simple_vacopy, rust_valist_struct_member,
+    rust_simple_vacopy, rust_valist_struct_member, rust_valist_struct_pointer_member,
 };
 
 use libc::c_char;
@@ -20,6 +20,8 @@ extern "C" {
 
     fn valist_struct_member(_: *const c_char, ...);
 
+    fn valist_struct_pointer_member(_: *const c_char, ...);
+
     fn restart_valist(_: *const c_char, ...);
 
     fn sample_stddev(count: i32, ...) -> f64;
@@ -69,6 +71,14 @@ pub fn test_valist_struct_member() {
     }
 }
 
+pub fn test_valist_struct_pointer_member() {
+    let fmt_str = CString::new("%d, %f\n").unwrap();
+    unsafe {
+        valist_struct_pointer_member(fmt_str.as_ptr(), 10, 1.5);
+        rust_valist_struct_pointer_member(fmt_str.as_ptr(), 10, 1.5);
+    }
+}
+
 pub fn test_restart_valist() {
     let fmt_str = CString::new("%d, %f\n").unwrap();
     unsafe {

tests/items/src/varargs.c

@@ -73,11 +73,27 @@ struct vastruct {
 
 // pattern first seen in apache (util_script.c)
 void valist_struct_member(const char *fmt, ...) {
-  struct vastruct thestruct;
+  struct vastruct a, b;
+
+  va_start(a.args, fmt);
+  va_copy(b.args, a.args);
+  vprintf(fmt, a.args);
+  vprintf(fmt, b.args);
+  va_end(a.args);
+  va_end(b.args);
+}
 
-  va_start(thestruct.args, fmt);
-  vprintf(fmt, thestruct.args);
-  va_end(thestruct.args);
+// pattern first seen in graphviz (sftable.c)
+void valist_struct_pointer_member(const char *fmt, ...) {
+  struct vastruct a, b;
+  struct vastruct *p = &a, *q = &b;
+
+  va_start(p->args, fmt);
+  va_copy(q->args, p->args);
+  vprintf(fmt, p->args);
+  vprintf(fmt, q->args);
+  va_end(p->args);
+  va_end(q->args);
 }
 
 // mirrors pattern from json-c's sprintbuf