| Message ID | 20220316055840.727571-16-richard.henderson@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | target/m68k: Conditional traps + trap cleanup | expand |
Hello Richard,
being mainly a Pascal programmer,
I always jump when I see such constructs:
You change the type of the print_syscall_err parameter to abi_ulong,
with is an unsigned type as the name suggests,
and after you compare it to a signed constant -4096.
This would never work in Pascal, but this is of course C code.
Nevertheless, I tried:
muller@gcc140:~/pas/check$ cat ./test-unsigned-int.c
#include <stdio.h>
int test_is_error (unsigned int u)
{
return (u > -4096);
}
int main ()
{
unsigned int v;
int error_count = 0;
v = (unsigned int) - 3000;
if (test_is_error(v) != 0)
printf("v=-3000 accepted\n");
else
error_count++;
v = (unsigned int) - 5000;
if (test_is_error(v) == 0)
printf("v=-5000 rejected\n");
else
error_count++;
v = (unsigned int) 0xfffffff0;
if (test_is_error(v) != 0)
printf("v=%d accepted\n",v);
else
error_count++;
if (test_is_error(0xffffff00) != 0)
printf("v=%d accepted\n",0xffffff00);
else
error_count++;
return error_count;
}
muller@gcc140:~/pas/check$ gcc -W -o test-unsigned-int test-unsigned-int.c
test-unsigned-int.c: In function ‘test_is_error’:
test-unsigned-int.c:5:13: warning: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Wsign-compare]
5 | return (u > -4096);
| ^
The results are OK (both for 32 and 64 bit executables),
but is there a cleaner way, which does not generate a warning, to write this?
Adding an explicit typecast to -4096 seems sufficient to silence that warning.
Pierre Muller
Le 16/03/2022 à 06:58, Richard Henderson a écrit :
> Errors are not all negative numbers, but only the top 4k.
>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> linux-user/strace.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/strace.c b/linux-user/strace.c
> index 2cdbf030ba..f235118fb6 100644
> --- a/linux-user/strace.c
> +++ b/linux-user/strace.c
> @@ -684,12 +684,12 @@ print_ipc(void *cpu_env, const struct syscallname *name,
> */
>
> static bool
> -print_syscall_err(abi_long ret)
> +print_syscall_err(abi_ulong ret)
> {
> const char *errstr;
>
> qemu_log(" = ");
> - if (ret < 0) {
> + if (ret > -4096) {
> errstr = target_strerror(-ret);
> if (errstr) {
> qemu_log("-1 errno=%d (%s)", (int)-ret, errstr);
diff --git a/linux-user/strace.c b/linux-user/strace.c index 2cdbf030ba..f235118fb6 100644 --- a/linux-user/strace.c +++ b/linux-user/strace.c @@ -684,12 +684,12 @@ print_ipc(void *cpu_env, const struct syscallname *name, */ static bool -print_syscall_err(abi_long ret) +print_syscall_err(abi_ulong ret) { const char *errstr; qemu_log(" = "); - if (ret < 0) { + if (ret > -4096) { errstr = target_strerror(-ret); if (errstr) { qemu_log("-1 errno=%d (%s)", (int)-ret, errstr);