[libcxx-commits] [libcxx] 422cf2b - [SystemZ][z/OS] Fix warnings from unsigned int to long in 32-bit mode

[Zbigniew Sarbinowski via libcxx-commits]

Author: Zbigniew Sarbinowski
Date: 2021-11-16T13:51:35Z
New Revision: 422cf2b506c1240def78b9a5e5b7f32abbcff243

URL: https://github.com/llvm/llvm-project/commit/422cf2b506c1240def78b9a5e5b7f32abbcff243
DIFF: https://github.com/llvm/llvm-project/commit/422cf2b506c1240def78b9a5e5b7f32abbcff243.diff

LOG: [SystemZ][z/OS] Fix warnings from unsigned int to long in 32-bit mode

This patch fixes the warnings which shows up when libcxx library started to be compiled in 32-bit mode on z/OS.
More specifically, the assignment from unsigned int to time_t aka long was flags as follows:
 ```
libcxx/include/c++/v1/__support/ibm/nanosleep.h:31:11: warning: implicit conversion changes signedness: 'unsigned int' to 'time_t' (aka 'long') [-Wsign-conversion]
  __sec = sleep(static_cast<unsigned int>(__sec));
        ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libcxx/include/c++/v1/__support/ibm/nanosleep.h:36:36: warning: implicit conversion changes signedness: 'unsigned int' to 'long' [-Wsign-conversion]
      __rem->tv_nsec = __micro_sec * 1000;
                     ~ ~~~~~~~~~~~~^~~~~~
libcxx/include/c++/v1/__support/ibm/nanosleep.h:47:36: warning: implicit conversion changes signedness: 'unsigned int' to 'long' [-Wsign-conversion]
      __rem->tv_nsec = __micro_sec * 1000;
                     ~ ~~~~~~~~~~~~^~~~~~
3 warnings generated.
```

Here is a small test case illustrating the issue:

```
typedef long    time_t ;
unsigned int sleep(unsigned int );
int main() {
  time_t sec = 0;
#ifdef FIX
  sec = static_cast<time_t>(sleep(static_cast<unsigned int>(sec)));
#else
  sec = sleep(static_cast<unsigned int>(sec));
#endif
}
```
clang++ -c -Wsign-conversion -m32 t.C
```
t.C:8:9: warning: implicit conversion changes signedness: 'unsigned int' to 'time_t' (aka 'long') [-Wsign-conversion]
  sec = sleep(static_cast<unsigned int>(sec));
      ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reviewed By: ldionne, #libc, Quuxplusone, Mordante

Differential Revision: https://reviews.llvm.org/D112837

Added: 
    

Modified: 
    libcxx/include/__support/ibm/nanosleep.h

Removed: 
    


################################################################################
diff  --git a/libcxx/include/__support/ibm/nanosleep.h b/libcxx/include/__support/ibm/nanosleep.h
index ec6379b8a9fa2..9c6b976c00030 100644
--- a/libcxx/include/__support/ibm/nanosleep.h
+++ b/libcxx/include/__support/ibm/nanosleep.h
@@ -21,14 +21,13 @@ inline int nanosleep(const struct timespec* __req, struct timespec* __rem) {
     errno = EINVAL;
     return -1;
   }
-  useconds_t __micro_sec =
-      static_cast<useconds_t>((__req->tv_nsec + 999) / 1000);
+  long __micro_sec = (__req->tv_nsec + 999) / 1000;
   time_t __sec = __req->tv_sec;
   if (__micro_sec > 999999) {
     ++__sec;
     __micro_sec -= 1000000;
   }
-  __sec = sleep(static_cast<unsigned int>(__sec));
+  __sec = static_cast<time_t>(sleep(static_cast<unsigned int>(__sec)));
   if (__sec) {
     if (__rem) {
       // Updating the remaining time to sleep in case of unsuccessful call to sleep().
@@ -39,7 +38,7 @@ inline int nanosleep(const struct timespec* __req, struct timespec* __rem) {
     return -1;
   }
   if (__micro_sec) {
-    int __rt = usleep(__micro_sec);
+    int __rt = usleep(static_cast<unsigned int>(__micro_sec));
     if (__rt != 0 && __rem) {
       // The usleep() does not provide the amount of remaining time upon its failure,
       // so the time slept will be ignored.