[profile] use GetComputerNameExW instead of gethostname on Windows

[inglorion]

Summary

In profile data paths, we replace "%h" with the hostname of the machine the program is running on. On Windows, we used gethostname() to obtain the hostname. This requires linking with ws2_32. With this change, we instead get the hostname from GetComputerNameExW(), which does not require ws2_32.

[inglorion]

This was suggested by @amccarth on D27086.

[rnk]

lib/profile/InstrProfilingPort.h

18 ↗

(On Diff #79474)

This code seems to go out of its way to not include windows.h, I'd like to preserve that. Can we sink the implementation of compiler_rt_gethostname to a .c file?

[inglorion]

lib/profile/InstrProfilingPort.h

18 ↗

(On Diff #79474)

Good point, will do.

[inglorion]

Moved the implementation of the compatibility function to a .c file, as requested by @rnk.

[amccarth]

I like where this is going.

lib/profile/InstrProfilingUtil.c

71 ↗

(On Diff #79477)

TCHAR?! Since we're calling WideCharToMultiByte, it seems we're assuming "Unicode" mode, so I'd write WCHAR and keep it explicit.

82 ↗

(On Diff #79477)

This doesn't terminate Name. There's a gotcha in this API that if you provide the length for the input string (BufferSize here), it'll process exactly that many "characters" and not terminate the output string.

See the description of cchWideChar in https://msdn.microsoft.com/en-us/library/windows/desktop/dd374130(v=vs.85).aspx

If you know that Buffer is terminated, then it's safest to use -1 for cchWideChar.

[inglorion]

addressed problems pointed out by @amccarth

[amccarth]

I'm happy. Thanks for fixing those warning messages, too.

[zturner]

lib/profile/InstrProfilingUtil.c

71 ↗

(On Diff #79477)

If we're assuming unicode mode, then let's call GetComputeNameExW.

[inglorion]

Changed to use GetComputerNameExW. Thanks for all the suggestions!

[inglorion]

clang-format

compiler-rt/trunk/lib/profile/InstrProfilingFile.c

else {
     lprofCurFilename.OwnsFilenamePat = 1;
   }
   /* Check the filename for "%p", which indicates a pid-substitution. */
   for (I = 0; FilenamePat[I]; ++I)
     if (FilenamePat[I] == '%') {
       if (FilenamePat[++I] == 'p') {
         if (!NumPids++) {
           if (snprintf(PidChars, MAX_PID_SIZE, "%d", getpid()) <= 0) {
-            PROF_WARN(
-                "Unable to parse filename pattern %s. Using the default name.",
+            PROF_WARN("Unable to get pid for filename pattern %s. Using the "
+                      "default name.",
                       FilenamePat);
             return -1;
           }
         }
       } else if (FilenamePat[I] == 'h') {
         if (!NumHosts++)
           if (COMPILER_RT_GETHOSTNAME(Hostname, COMPILER_RT_MAX_HOSTLEN)) {
-            PROF_WARN(
-                "Unable to parse filename pattern %s. Using the default name.",
+            PROF_WARN("Unable to get hostname for filename pattern %s. Using "
+                      "the default name.",
                       FilenamePat);
             return -1;
           }
       } else if (containsMergeSpecifier(FilenamePat, I)) {
         if (MergingEnabled) {
           PROF_WARN("%%m specifier can only be specified once in %s.\n",
                     FilenamePat);
           return -1;
         }

compiler-rt/trunk/lib/profile/InstrProfilingPort.h

 
 #ifdef _MSC_VER
 #define COMPILER_RT_SECTION(Sect) __declspec(allocate(Sect))
 #else
 #define COMPILER_RT_SECTION(Sect) __attribute__((section(Sect)))
 #endif
 
 #define COMPILER_RT_MAX_HOSTLEN 128
-#ifdef _MSC_VER
-#define COMPILER_RT_GETHOSTNAME(Name, Len) gethostname(Name, Len)
-#elif defined(__ORBIS__)
+#ifdef __ORBIS__
 #define COMPILER_RT_GETHOSTNAME(Name, Len) ((void)(Name), (void)(Len), (-1))
 #else
 #define COMPILER_RT_GETHOSTNAME(Name, Len) lprofGetHostName(Name, Len)
+#ifndef _MSC_VER
 #define COMPILER_RT_HAS_UNAME 1
 #endif
+#endif
 
 #if COMPILER_RT_HAS_ATOMICS == 1
 #ifdef _MSC_VER
 #include <windows.h>
 #if _MSC_VER < 1900
 #define snprintf _snprintf
 #endif
 #if defined(_WIN64)

compiler-rt/trunk/lib/profile/InstrProfilingUtil.c

 void *lprofPtrFetchAdd(void **Mem, long ByteIncr) {
   void *Old = *Mem;
   *((char **)Mem) += ByteIncr;
   return Old;
 }
 
 #endif
 
-#ifdef COMPILER_RT_HAS_UNAME
+#ifdef _MSC_VER
+COMPILER_RT_VISIBILITY int lprofGetHostName(char *Name, int Len) {
+  WCHAR Buffer[COMPILER_RT_MAX_HOSTLEN];
+  DWORD BufferSize = sizeof(Buffer);
+  BOOL Result =
+      GetComputerNameExW(ComputerNameDnsFullyQualified, Buffer, &BufferSize);
+  if (!Result)
+    return -1;
+  if (WideCharToMultiByte(CP_UTF8, 0, Buffer, -1, Name, Len, NULL, NULL) == 0)
+    return -1;
+  return 0;
+}
+#elif defined(COMPILER_RT_HAS_UNAME)
 COMPILER_RT_VISIBILITY int lprofGetHostName(char *Name, int Len) {
   struct utsname N;
   int R;
   if (!(R = uname(&N)))
     strncpy(Name, N.nodename, Len);
   return R;
 }
 #endif