[PATCH] selftests/net: use MAP_FAILED instead of (void *)-1 in tcp_mmap

[longlong yan]

mmap() is documented to return MAP_FAILED on error, but tcp_mmap.c
compares the return value against (void *)-1 and (unsigned char *)-1.

Replace these with the standard MAP_FAILED macro for better readability
and type safety.

Signed-off-by: longlong yan <yanlongl...@kylinos.cn>
---
 tools/testing/selftests/net/tcp_mmap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/net/tcp_mmap.c 
b/tools/testing/selftests/net/tcp_mmap.c
index 2544ae35d07a..487ae659a1f1 100644
--- a/tools/testing/selftests/net/tcp_mmap.c
+++ b/tools/testing/selftests/net/tcp_mmap.c
@@ -141,12 +141,12 @@ static void *mmap_large_buffer(size_t need, size_t 
*allocated)
        buffer = mmap(NULL, sz, PROT_READ | PROT_WRITE,
                      MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
 
-       if (buffer == (void *)-1) {
+       if (buffer == MAP_FAILED) {
                sz = need;
                buffer = mmap(NULL, sz, PROT_READ | PROT_WRITE,
                              MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE,
                              -1, 0);
-               if (buffer != (void *)-1)
+               if (buffer != MAP_FAILED)
                        fprintf(stderr, "MAP_HUGETLB attempt failed, look at 
/sys/kernel/mm/hugepages for optimal performance\n");
        }
        *allocated = sz;
@@ -189,13 +189,13 @@ void *child_thread(void *arg)
 
        fcntl(fd, F_SETFL, O_NDELAY);
        buffer = mmap_large_buffer(chunk_size, &buffer_sz);
-       if (buffer == (void *)-1) {
+       if (buffer == MAP_FAILED) {
                perror("mmap");
                goto error;
        }
        if (zflg) {
                raddr = mmap(NULL, chunk_size + map_align, PROT_READ, flags, 
fd, 0);
-               if (raddr == (void *)-1) {
+               if (raddr == MAP_FAILED) {
                        perror("mmap");
                        zflg = 0;
                } else {
@@ -547,7 +547,7 @@ int main(int argc, char *argv[])
        }
 
        buffer = mmap_large_buffer(chunk_size, &buffer_sz);
-       if (buffer == (unsigned char *)-1) {
+       if (buffer == MAP_FAILED) {
                perror("mmap");
                exit(1);
        }
-- 
2.43.0