qemu-hppa log10 produces incorrect results

Host environment

• Operating system: Gentoo Linux (x86-64)
• OS/kernel version: 6.12.16-gentoo-dist
• Architecture: x86-64
• QEMU flavor: qemu-hppa
• QEMU version: 10.0.3
• systemd-nspawn environment running qemu via binfmt-misc

Emulated/Virtualized environment

• Operating system: Gentoo Linux (hppa1.1)
• Architecture: hppa1.1

Description of problem

The build of flex fails in the emulated environment (with stage1flex aborting), see https://bugs.gentoo.org/962007

Reducing the code to a minimal reproducer led to the following program:

#include <math.h>
#include <stdio.h>

int main() {
  for (int i = 1; i <= 50; i++) {
    int c=ceil (log10(i));
    printf("%d   %d\n", i, c);
  }
}

It can be compiled with

dilfridge@dilfridge-hppa ~ $ gcc -march=1.1 -o mylist mylist.c -lm -static

(static or dynamic linking makes no difference, indicating that glibc is not the problem).

Running natively on a PA-RISC machine, the output is

g-dilfridge@matoro-hppadev ~ $ ./mylist
1   0
2   1
3   1
4   1
5   1
6   1
7   1
8   1
9   1
10   1
11   2
12   2
13   2
14   2
15   2
16   2
17   2
18   2
19   2
20   2
21   2
22   2
23   2
24   2
25   2
26   2
27   2
28   2
29   2
30   2
31   2
32   2
33   2
34   2
35   2
36   2
37   2
38   2
39   2
40   2
41   2
42   2
43   2
44   2
45   2
46   2
47   2
48   2
49   2
50   2

Under qemu-hppa, the output is

dilfridge@dilfridge-hppa ~ $ ./mylist 
1   0
2   1
3   2
4   2
5   3
6   3
7   3
8   3
9   4
10   4
11   4
12   4
13   4
14   4
15   4
16   4
17   -3643122
18   5
19   5
20   5
21   5
22   5
23   5
24   5
25   5
26   5
27   5
28   5
29   5
30   5
31   5
32   5
33   -1821558
34   -3643121
35   6
36   6
37   6
38   6
39   6
40   6
41   6
42   6
43   6
44   6
45   6
46   6
47   6
48   6
49   6
50   6

This may be related to #625