better detection of broken -fzero-call-used-regs

gcc 13.2.0 on ppc64le refuses to compile some function, including
cipher.c:compression_alg_list() with an error:

> sorry, unimplemented: argument ‘used’ is not supportedcw
> for ‘-fzero-call-used-regs’ on this target

This extends the autoconf will-it-work test with a similarly-
structured function that seems to catch this.

Spotted/tested by Colin Watson; bz3645

diff --git a/m4/openssh.m4 b/m4/openssh.m4
index 5d4c56280fce211715eb6aa72eb5beddb301d4c3..033df501c3d80772d376d6ad0b26ea493a3bb58c 100644 (file)
--- a/m4/openssh.m4
+++ b/m4/openssh.m4
@@ -20,18 +20,24 @@ char *f2(char *s, ...) {
        va_end(args);
        return strdup(ret);
 }
+const char *f3(int s) {
+       return s ? "good" : "gooder";
+}
 int main(int argc, char **argv) {
-       (void)argv;
        char b[256], *cp;
+       const char *s;
        /* Some math to catch -ftrapv problems in the toolchain */
        int i = 123 * argc, j = 456 + argc, k = 789 - argc;
        float l = i * 2.1;
        double m = l / 0.5;
        long long int n = argc * 12345LL, o = 12345LL * (long long int)argc;
+       (void)argv;
        f(1);
-       snprintf(b, sizeof b, "%d %d %d %f %f %lld %lld\n", i,j,k,l,m,n,o);
+       s = f3(f(2));
+       snprintf(b, sizeof b, "%d %d %d %f %f %lld %lld %s\n", i,j,k,l,m,n,o,s);
        if (write(1, b, 0) == -1) exit(0);
-       cp = f2("%d %d %d %f %f %lld %lld\n", i,j,k,l,m,n,o);
+       cp = f2("%d %d %d %f %f %lld %lld %s\n", i,j,k,l,m,n,o,s);
+       if (write(1, cp, 0) == -1) exit(0);
        free(cp);
        /*
         * Test fallthrough behaviour.  clang 10's -Wimplicit-fallthrough does