Bug 23699 – ImportC: Unclear documentation that struct/union/enum introduce implicit typedefs

When compiling the test with `gcc -std=c11 -fsyntax-only` compilable/test22807.c:10:10: error: unknown type name ‘OldFashionedHeader’ 10 | int peek(OldFashionedHeader *head){ | ^~~~~~~~~~~~~~~~~~ Test content: ``` struct OldFashionedHeader { int n; // number of entries in buff char buff[1]; }; int peek(OldFashionedHeader *head){ if(head->n < 2) return 0; return head->buff[1]; // do not give array bounds error } ```

ImportC deals with tag name spaces like C++ does. I.e. they are distinct only if there is both a tag name declaration and a regular name declaration both in the same scope. It shouldn't cause any more trouble than using a C++ compiler to compile C code.

(In reply to Walter Bright from comment #1) > ImportC deals with tag name spaces like C++ does. I.e. they are distinct > only if there is both a tag name declaration and a regular name declaration > both in the same scope. > > It shouldn't cause any more trouble than using a C++ compiler to compile C > code. There is a passing reference to this under Tag Symbols https://dlang.org/spec/importc.html#tag-symbols It sort of gets lost in the ether as a lot of the focus of that section points to the ImportC limitations, rather than extensions.

The term used by C++ is "elaborated type specifier", which is used to distinguish between types and regular identifiers. For example, the following code is accepted by both C++ and ImportC ``` struct s { int a; }; void g(int s) { struct s* p = (struct s*)malloc(sizeof(struct s)); p->a = s; } ``` Whereas this is rejected by both C++ and ImportC, for the same reason. ``` struct s { int a; }; void g(int s) { s* p = (s*)malloc(sizeof(s)); p->a = s; } ```

@WalterBright created dlang/dlang.org pull request #3581 "fix Issue 23699 - ImportC: Unclear documentation that struct/union/en…" fixing this issue: - fix Issue 23699 - ImportC: Unclear documentation that struct/union/enum introduce implicit typedefs https://github.com/dlang/dlang.org/pull/3581

dlang/dlang.org pull request #3581 "fix Issue 23699 - ImportC: Unclear documentation that struct/union/en…" was merged into master: - 5cbb87c50a592154f72f8cf71446b76ad057f1a8 by Walter Bright: fix Issue 23699 - ImportC: Unclear documentation that struct/union/enum introduce implicit typedefs https://github.com/dlang/dlang.org/pull/3581