On 2025-01-28 06:27, Jacob Bachmeyer wrote:
On 1/26/25 10:59, Torbjorn SVENSSON wrote:
Hi Jacub,
Thanks for the review.
You are welcome. A V2 will probably be requested (or I might just do it
and credit you for the initial patch) but whether to preserve backwards
compatibility or modernize the whole file is yet to be decided.
On 2025-01-26 02:51, Jacob Bachmeyer wrote:
On 1/25/25 02:55, Torbjörn SVENSSON wrote:
[...]
As I understand, this is a shift in C dialect over the years if it is
a real issue. Originally, an empty argument list did not mean "no
arguments" but "unspecified arguments". To declare "no arguments"
you must explicitly write "func(void)" in C.
It was like this, but with C23, it's no longer the case.
Do I correctly understand that C23 also removed the K&R function
definition syntax? If so, testglue.c needs a lot more work than just a
few prototypes...
I'm not an expert on the specifications, but from what I can understand of the
Wikipedia article and the foot notes, I would say that the K&R style cannot be
used in C23.
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2510.pdf
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2432.pdf
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2841.htm
In C23, it's considered an error to call a function where the function
prototype does not match the call site (only exception to this is the
elipse AFAIK).
The ellipsis indicates varargs, so any number of arguments "match" the
ellipsis. :-)
Indeed, I just wanted to make that part explicit. :)
While I seem to recall that the C standard has always specified
exit(3) to take an "int" argument, it was also implicitly intended
for programs hosted on Unix and a freestanding board might not use an
exit code and simply halt or shut down when "exit()" is called.
I don't know if you are allowed to define "exit()" (without arguments)
and still be complaint with the C standard. If you are not complaint
with the C standard, then all bets are off. :)
For a function like exit() or _exit() that does not return, calling a
"func(void)" implementation as if it were "func(int)" should do no
harm. For most calling conventions, even doing that with a function
that *does* return should work; the exceptions are conventions where the
callee cleans up arguments passed on the stack.
I can add it to those functions, but in C23, there is no requirement on that. Having
nothing within the parenthesis is equal to writing "void" in them.
If you want the code to work more or less in the same grey zone as
before, I guess it could change to this:
#if __STDC_VERSION__ >= 202311L
extern void REAL_EXIT (int);
#else
extern void REAL_EXIT ();
#endif
I can send a V2 with this if you think that is better.
I will want a V2 in any case, but we may only need "#ifdef __STDC__"
instead of testing __STDC_VERSION__. Also, if adding explicit
prototypes, REAL_ABORT should explicitly take "(void)".
I don't think that checking __STDC__ is going to work:
$ diff -u0 <(echo | arm-none-eabi-gcc -dM -x c -E -o - -std=c17 - ) <(echo |
arm-none-eabi-gcc -dM -x c -E -o - -std=c23 - )
--- /dev/fd/63 2025-01-28 09:04:36.687223645 +0000
+++ /dev/fd/62 2025-01-28 09:04:36.687223645 +0000
@@ -94,0 +95 @@
+#define __CHAR8_TYPE__ unsigned char
@@ -267 +268 @@
-#define __STDC_VERSION__ 201710L
+#define __STDC_VERSION__ 202311L
@@ -301,0 +303 @@
+#define __GCC_ATOMIC_CHAR8_T_LOCK_FREE 1
Kind regards,
Torbjörn
This also looks like you might actually know what testglue.c actually
does and how it is used. Could you enlighten me on that or at least
point me to an example of something that uses it? I am currently
reluctant to touch it because I do not know what changing it might
break.
The testglue.c is used whenever you need to get status of a test case,
but you cannot get the exit code directly by invoking the test
application. A typical example is when you use a simulator or run
tests on an embedded target though a GDB server.
While running the gcc testsuite, you would specify that the testglue.c
file is needed in your board definition using:
set_board_info needs_status_wrapper 1
This will build the testglue.c to an object file before the tests are
started and then include the object file in the link phase of every
executable.
[...]
The technique used to override exit, abort and main using the --wrap
argument to the GNU linker.
There is probably a lot more details that I've missed here to why it's
implemented the way it is, but at least this gives you an idea of when
and why it's may be needed.
Aha! Now the code in that file makes sense to me.
-- Jacob
