Re: Gnulib's tempname.c does not compile with TCC: max_align_t undefined

[Bruno Haible]

Luca Saiu wrote:
> It is the version packaged by debian:
> 
> [luca@moore ~]$ tcc --version
> tcc version 0.9.27 (x86_64 Linux)

OK.

I can see that the max_align_t problem is the only compilation error in
all of gnulib (excluding C++ sources).

The max_align_t problem comes from two causes:

1) tcc's <stddef.h> does not define max_align_t. Gnulib's autoconfiguration
   notices it and sets HAVE_MAX_ALIGN_T=0 and activates the <stddef.h>
   replacement.

2) When tcc processes this source file

   #include <config.h>
   #include <sys/types.h>
   #ifdef __need_size_t
   bbb
   #endif
   #include <stddef.h>

   the preprocessed output contains the token 'bbb'. This means that tcc's
   <stddef.h> does not obey the special invocation convention that some
   glibc header files assume. For example, glibc's <time.h> does

   /* Get size_t and NULL from <stddef.h>.  */
   # define __need_size_t
   # define __need_NULL
   # include <stddef.h>

   The expectation is that once the include of <stddef.h> is terminated,
   the symbols __need_size_t, __need_NULL are not defined any more. So
   that when other code does
     #include <stddef.h>
   the entire <stddef.h> contents will be included.

I'm committing this workaround. I wouldn't be surprised if the same
problem would also occur for
  fcntl.h
  signal.h
  stdio.h
  stdlib.h
  sys/types.h
  time.h
  wchar.h


2021-03-02  Bruno Haible  <bruno@clisp.org>

        stddef: Work around an interoperability problem of tcc with glibc.
        Reported by Luca Saiu <positron@gnu.org> in
        <https://lists.gnu.org/archive/html/bug-gnulib/2021-03/msg00011.html>.
        * lib/stddef.in.h [__TINYC__]: In case of the special invocation
        convention, undefine the macros that TinyCC's <stddef.h> should undefine
        but doesn't.
        * doc/posix-headers/stddef.texi: Mention the TinyCC bug.

diff --git a/doc/posix-headers/stddef.texi b/doc/posix-headers/stddef.texi
index dbc0103..ba27fa8 100644
--- a/doc/posix-headers/stddef.texi
+++ b/doc/posix-headers/stddef.texi
@@ -27,6 +27,10 @@ NetBSD 5.0
 Some platforms provide a @code{NULL} macro whose value does not have the size
 of a pointer:
 AIX 7.2 with xlc in 64-bit mode.
+
+@item
+When this header file is provided by TinyCC 0.9.27 on glibc systems, it does
+not fulfil the expectations of other glibc header files.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/lib/stddef.in.h b/lib/stddef.in.h
index ba6f903..590e12c 100644
--- a/lib/stddef.in.h
+++ b/lib/stddef.in.h
@@ -42,6 +42,15 @@
 #   define _GL_STDDEF_WINT_T
 #  endif
 #  @INCLUDE_NEXT@ @NEXT_STDDEF_H@
+   /* On TinyCC, make sure that the macros that indicate the special invocation
+      convention get undefined.  */
+#  ifdef __TINYC__
+#   undef __need_wchar_t
+#   undef __need_size_t
+#   undef __need_ptrdiff_t
+#   undef __need_NULL
+#   undef __need_wint_t
+#  endif
 # endif
 
 #else