Report Windows error code in a fatal error after a system call

[probinson]

Summary

We've had two reports in the past year that CryptAcquireContextW failed; but without the Windows error code it's hard to know what's going on.

[bcraig]

Looks good to me, but since this is in the LLVMSupport library, you should probably add llvm-commits to the subscriber list.

[aaron.ballman]

LGTM with a nit.

Also, I am really curious to know why CryptAcquireContext fails in those cases!

lib/Support/Windows/Process.inc

421

msg should be Msg for style conventions.

[probinson]

In D14583#287406, @bcraig wrote:

Looks good to me, but since this is in the LLVMSupport library, you should probably add llvm-commits to the subscriber list.

Ah, right, I should have. But I'm not seeing how to add subscribers post-facto.

In D14583#287407, @aaron.ballman wrote:

LGTM with a nit.

Also, I am really curious to know why CryptAcquireContext fails in those cases!

Me too. Once is a fluke, twice is a trend. Probably some obscure system-resource problem but it would be nice to be sure.

lib/Support/Windows/Process.inc

421

The prevailing style in this file is for lowercase parameter names, but I guess we gotta start somewhere!

[probinson]

r252800, thanks!

[gbedwell]

Also, I am really curious to know why CryptAcquireContext fails in those cases!

Me too. Once is a fluke, twice is a trend. Probably some obscure system-resource problem but it would be nice to be sure.

I'm out of the office this week, so can't test, but I'm pretty sure you can reproduce this by spawning clang in an environment where the SYSTEMROOT environment variable has not been propagated (or by running it from a cmd window after typing "set SYSTEMROOT=".

lib/Support/Windows/Process.inc

 }
 
 const char *Process::ResetColor() {
   if (UseANSI) return "\033[0m";
   SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), defaultColors());
   return 0;
 }
 
+// Include GetLastError() in a fatal error message.
+static void ReportLastErrorFatal(const char *msg) {
+  std::string ErrMsg;
+  MakeErrMsg(&ErrMsg, msg);
+  report_fatal_error(ErrMsg);
+}
+
 unsigned Process::GetRandomNumber() {
   HCRYPTPROV HCPC;
   if (!::CryptAcquireContextW(&HCPC, NULL, NULL, PROV_RSA_FULL,
                               CRYPT_VERIFYCONTEXT))
-    report_fatal_error("Could not acquire a cryptographic context");
+    ReportLastErrorFatal("Could not acquire a cryptographic context");
 
   ScopedCryptContext CryptoProvider(HCPC);
   unsigned Ret;
   if (!::CryptGenRandom(CryptoProvider, sizeof(Ret),
                         reinterpret_cast<BYTE *>(&Ret)))
-    report_fatal_error("Could not generate a random number");
+    ReportLastErrorFatal("Could not generate a random number");
   return Ret;
 }