[OpenMP] Fix incorrect KMP_STRLEN() macro on Windows

[jlpeyton]

Summary

The second argument to the strnlen_s(str, size) function should be sizeof(str) when str is a true array of characters with known size (instead of just a char*).
Use type traits to determine if first parameter is character array and use the correct size based on that trait.

[AndreyChurbanov]

LGTM

openmp/runtime/src/kmp_os.h

enum kmp_warnings_level {
   kmp_warnings_explicit = 6, /* Explicitly set to ON - more warnings */
   kmp_warnings_verbose /* reserved */
 };
 
 #ifdef __cplusplus
 } // extern "C"
 #endif // __cplusplus
 
+// Safe C API
+#include "kmp_safe_c_api.h"
+
 // Macros for C++11 atomic functions
 #define KMP_ATOMIC_LD(p, order) (p)->load(std::memory_order_##order)
 #define KMP_ATOMIC_OP(op, p, v, order) (p)->op(v, std::memory_order_##order)
 
 // For non-default load/store
 #define KMP_ATOMIC_LD_ACQ(p) KMP_ATOMIC_LD(p, acquire)
 #define KMP_ATOMIC_LD_RLX(p) KMP_ATOMIC_LD(p, relaxed)
 #define KMP_ATOMIC_ST_REL(p, v) KMP_ATOMIC_OP(store, p, v, release)

 #define KMP_DLSYM(name) __kmp_lookup_symbol(name)
 #define KMP_DLSYM_NEXT(name) nullptr
 #else
 #define KMP_DLSYM(name) dlsym(RTLD_DEFAULT, name)
 #define KMP_DLSYM_NEXT(name) dlsym(RTLD_NEXT, name)
 #endif
 
 #endif /* KMP_OS_H */
-// Safe C API
-#include "kmp_safe_c_api.h"

openmp/runtime/src/kmp_safe_c_api.h

 
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef KMP_SAFE_C_API_H
 #define KMP_SAFE_C_API_H
 
+#include <type_traits>
 #include "kmp_platform.h"
 #include <string.h>
 
 // Replacement for banned C API
 
 // Not every unsafe call listed here is handled now, but keeping everything
 // in one place should be handy for future maintenance.
 #if KMP_OS_WINDOWS && KMP_MSVC_COMPAT
 
 #define RSIZE_MAX_STR (4UL << 10) // 4KB
 
 // _malloca was suggested, but it is not a drop-in replacement for _alloca
 #define KMP_ALLOCA _alloca
 
 #define KMP_MEMCPY_S memcpy_s
 #define KMP_SNPRINTF sprintf_s
 #define KMP_SSCANF sscanf_s
 #define KMP_STRCPY_S strcpy_s
 #define KMP_STRNCPY_S strncpy_s
 
 // Use this only when buffer size is unknown
 #define KMP_MEMCPY(dst, src, cnt) memcpy_s(dst, cnt, src, cnt)
 
-#define KMP_STRLEN(str) strnlen_s(str, RSIZE_MAX_STR)
+template <typename T, bool B = std::is_array<T>::value>
+struct kmp_get_rmax_t {};
+template <typename T> struct kmp_get_rmax_t<T, false> {
+  static const size_t value = RSIZE_MAX_STR;
+};
+template <typename T> struct kmp_get_rmax_t<T, true> {
+  static const size_t value = sizeof(T);
+};
+#define KMP_STRLEN(str) strnlen_s(str, kmp_get_rmax_t<decltype(str)>::value)
 
 // Use this only when buffer size is unknown
 #define KMP_STRNCPY(dst, src, cnt) strncpy_s(dst, cnt, src, cnt)
 
 // _TRUNCATE insures buffer size > max string to print.
 #define KMP_VSNPRINTF(dst, cnt, fmt, arg)                                      \
   vsnprintf_s(dst, cnt, _TRUNCATE, fmt, arg)