[test] Use printf instead of C++ iostream, NFC.

[Hahnfeld]

Summary

This test fails with libc++ when built with MemorySanitizer. This
is because we link to an uninstrumented version of the library
so msan detects a nested error when calling std::cout << "...".
This can be easily avoided by using good old printf.

[vsk]

Thanks, LGTM. So, am I understanding correctly that there are msan interceptors for printf, but not iostream?

[Hahnfeld]

In D49867#1177081, @vsk wrote:

Thanks, LGTM. So, am I understanding correctly that there are msan interceptors for printf, but not iostream?

I'm not sure that there are interceptors for printf. I think the problem was that instrumented and inlined code from headers got mixed with uninstrumented code from the shared library.

[vsk]

In D49867#1177087, @Hahnfeld wrote:

In D49867#1177081, @vsk wrote:

Thanks, LGTM. So, am I understanding correctly that there are msan interceptors for printf, but not iostream?

I'm not sure that there are interceptors for printf. I think the problem was that instrumented and inlined code from headers got mixed with uninstrumented code from the shared library.

Oh, whereas none of the printf logic is inline, so either all of it is instrumented or not instrumented. Sure, makes sense.

compiler-rt/trunk/test/ubsan/TestCases/Misc/monitor.cpp

 // RUN: %clangxx -w -fsanitize=bool %s -o %t
 // RUN: %run %t 2>&1 | FileCheck %s
 
 // __ubsan_on_report is not defined as weak. Redefining it here isn't supported
 // on Windows.
 //
 // UNSUPPORTED: win32
 // Linkage issue
 // XFAIL: openbsd
 
-#include <iostream>
+#include <cstdio>
 
 extern "C" {
 void __ubsan_get_current_report_data(const char **OutIssueKind,
                                      const char **OutMessage,
                                      const char **OutFilename,
                                      unsigned *OutLine, unsigned *OutCol,
                                      char **OutMemoryAddr);
 
 // Override the definition of __ubsan_on_report from the runtime, just for
 // testing purposes.
 void __ubsan_on_report(void) {
   const char *IssueKind, *Message, *Filename;
   unsigned Line, Col;
   char *Addr;
   __ubsan_get_current_report_data(&IssueKind, &Message, &Filename, &Line, &Col,
                                   &Addr);
 
-  std::cout << "Issue: " << IssueKind << "\n"
-            << "Location: " << Filename << ":" << Line << ":" << Col << "\n"
-            << "Message: " << Message << std::endl;
+  printf("Issue: %s\n", IssueKind);
+  printf("Location: %s:%u:%u\n", Filename, Line, Col);
+  printf("Message: %s\n", Message);
 
   (void)Addr;
 }
 }
 
 int main() {
   char C = 3;
   bool B = *(bool *)&C;
   // CHECK: Issue: invalid-bool-load
   // CHECK-NEXT: Location: {{.*}}monitor.cpp:[[@LINE-2]]:12
   // CHECK-NEXT: Message: Load of value 3, which is not a valid value for type 'bool'
   return 0;
 }