CVS commit: src/lib/libc/stdlib

["Kamil Rytarowski" <kamil%netbsd.org@localhost>]

Module Name:    src
Committed By:   kamil
Date:           Sat Feb 22 14:07:57 UTC 2020

Modified Files:
        src/lib/libc/stdlib: _rand48.c

Log Message:
Avoid undefined behavior in the rand48(3) implementation

Instead of implicid promotion to signed int,
explicitly cast the arguments to unsigned int.

_rand48.c:53:27, signed integer overflow:
58989 * 58970 cannot be represented in type 'int'

_rand48.c:53:38, signed integer overflow:
-2093025904 + -1496809120 cannot be represented in type 'int'

_rand48.c:53:57, signed integer overflow:
57068 * 42787 cannot be represented in type 'int'

New and old code produce the same code as tested with:

#include <stdio.h>
#include <stdlib.h>

#define COUNT 1000 * 1000

int
main(void)
{
        FILE *fp;
        int i;

        fp = fopen("numbers.txt", "w+");
        if (!fp)
                abort();

        for(i = 0; i < COUNT; i++) {
                fprintf(fp, "%f\n", drand48());
                fprintf(fp, "%ld\n", lrand48());
                fprintf(fp, "%ld\n", mrand48());
        }

        fclose(fp);

        return 0;
}


To generate a diff of this commit:
cvs rdiff -u -r1.8 -r1.9 src/lib/libc/stdlib/_rand48.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.