Make std::random_device retry after short reads

	PR libstdc++/65142
	* src/c++11/random.cc (random_device::_M_getval()): Retry after short
	reads.

git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@227872 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 17 insertions, 7 deletions

diff --git a/libstdc++-v3/src/c++11/random.cc b/libstdc++-v3/src/c++11/random.cc
index 1d102c755b2..f1d6125128a 100644
--- a/libstdc++-v3/src/c++11/random.cc
+++ b/libstdc++-v3/src/c++11/random.cc
@@ -130,16 +130,26 @@ namespace std _GLIBCXX_VISIBILITY(default)
 #endif
 
     result_type __ret;
-
+    void* p = &__ret;
+    size_t n = sizeof(result_type);
 #ifdef _GLIBCXX_HAVE_UNISTD_H
-    auto e = read(fileno(static_cast<FILE*>(_M_file)),
-		  static_cast<void*>(&__ret), sizeof(result_type));
+    do
+      {
+	const int e = read(fileno(static_cast<FILE*>(_M_file)), p, n);
+	if (e > 0)
+	  {
+	    n -= e;
+	    p = static_cast<char*>(p) + e;
+	  }
+	else if (e != -1 || errno != EINTR)
+	  __throw_runtime_error(__N("random_device could not be read"));
+      }
+    while (n > 0);
 #else
-    auto e = std::fread(static_cast<void*>(&__ret), sizeof(result_type),
-		        1, static_cast<FILE*>(_M_file));
+    const size_t e = std::fread(p, n, 1, static_cast<FILE*>(_M_file));
+    if (e != 1)
+      __throw_runtime_error(__N("random_device could not be read"));
 #endif
-    if (e != sizeof(result_type))
-      __throw_runtime_error(__N("random_device could not read enough bytes"));
 
     return __ret;
   }