source cleanup: remove all custom typedef structs

 - Stick to a single unified way to use structs
 - Make checksrc complain on 'typedef struct {'
 - Allow them in tests, public headers and examples

 - Let MD4_CTX, MD5_CTX, and SHA256_CTX typedefs remain as they actually
   typedef different types/structs depending on build conditions.

Closes #5338

1 files changed, 19 insertions, 0 deletions

diff --git a/docs/CODE_STYLE.md b/docs/CODE_STYLE.md
index 0ceb5b9ad..561343752 100644
--- a/docs/CODE_STYLE.md
+++ b/docs/CODE_STYLE.md
@@ -244,3 +244,22 @@ depending on a build-time conditional:
     #endif
 
     int content = magic(3);
+
+## No typedefed structs
+
+Use structs by all means, but do not typedef them. Use the `struct name` way
+of identifying them:
+
+    struct something {
+       void *valid;
+       size_t way_to_write;
+    };
+    struct something instance;
+
+**Not okay**:
+
+    typedef struct {
+       void *wrong;
+       size_t way_to_write;
+    } something;
+    something instance;