error.h: Be more careful with error code masking.

It should never happen that two or more of the three special high bits
(osl, lopsub, system) are set in an integer that stores a paraslash
error value, but gcc-12 can't prove this and complains as follows:

	error.h:304:28: warning: array subscript 268435456 is above array bounds of 'const char * const[220]' [-Warray-bounds]
	  304 |         return para_errlist[num];
	      |                ~~~~~~~~~~~~^~~~~

Avoid this warning by always clearing all three special bits.

diff --git a/error.h b/error.h
index fe44ff5c50487744881ea1d21d1007528a2ecd70..f2c6e15e41e7a77fd5b30312e5ae7118d0f2f0b6 100644 (file)
--- a/error.h
+++ b/error.h
@@ -303,18 +303,20 @@ static const char *weak_lls_strerror(int) __attribute__ ((weakref("lls_strerror"
  */
 _static_inline_ const char *para_strerror(int num)
 {
+       unsigned idx = num & ~((1U << OSL_ERROR_BIT) | (1U << LLS_ERROR_BIT)
+               | (1U << SYSTEM_ERROR_BIT));
        assert(num > 0);
        if (IS_OSL_ERROR(num)) {
                assert(weak_osl_strerror);
-               return weak_osl_strerror(num & ~(1U << OSL_ERROR_BIT));
+               return weak_osl_strerror(idx);
        }
        if (IS_LLS_ERROR(num)) {
                assert(weak_lls_strerror);
-               return weak_lls_strerror(num & ~(1U << LLS_ERROR_BIT));
+               return weak_lls_strerror(idx);
        }
        if (IS_SYSTEM_ERROR(num))
-               return strerror(num & ~(1U << SYSTEM_ERROR_BIT));
-       return para_errlist[num];
+               return strerror(idx);
+       return para_errlist[idx];
 }
 
 /**