[libfuzzer] Enable trace-malloc-unballanced.test on Windows.

[metzman]

Summary

Enables trace-malloc-unbalanced.test on Windows, fixing two problems it had with Windows before.
The first fix is specifying python instead of relying on a script's shebang since they can't be used on Windows.
The second fix is making the regex tolerate windows' implementation of the "%p" format string.

[metzman]

• Make comment more descriptive

[metzman]

Max could you please take a look when you get a chance (no rush).

This diff enables trace-malloc-unbalanced.test on Windows, fixing two problems it had with Windows before.
The first fix is specifying python instead of relying on a script's shebang since they can't be used on Windows.
The second fix is making the regex tolerate windows' implementation of the "%p" format string.
I don't think there is a nice way to emulate Linux's behavior, but if I see this problem is widespread, I'll revisit.

[Dor1s]

LGTM! I like your comment https://reviews.llvm.org/D51760#1226757, maybe you could paste it into the CL description too?

compiler-rt/test/fuzzer/trace-malloc-unbalanced.test

 // FIXME: This test infinite loops on darwin because it crashes
 // printing a stack trace repeatedly
-// FIXME: Disabled on Windows because of reliance on shebang line and failure.
-UNSUPPORTED: darwin, windows
+UNSUPPORTED: darwin
 
 // Verifies lib/fuzzer/scripts/unbalanced_allocs.py script
 
 RUN: %cpp_compiler %S/TraceMallocTest.cpp -o %t-TraceMallocTest
 
+# Specify python because we can't use the shebang line on Windows.
 RUN: %run %t-TraceMallocTest -seed=1 -trace_malloc=1 -runs=200 2>&1 | \
-RUN:    %libfuzzer_src/scripts/unbalanced_allocs.py --skip=5 | FileCheck %s
+RUN:    python %libfuzzer_src/scripts/unbalanced_allocs.py --skip=5 | FileCheck %s
 
 RUN: %run %t-TraceMallocTest -seed=1 -trace_malloc=2 -runs=200 2>&1 | \
-RUN:    %libfuzzer_src/scripts/unbalanced_allocs.py --skip=5 | FileCheck %s --check-prefixes=CHECK,CHECK2
+RUN:    python %libfuzzer_src/scripts/unbalanced_allocs.py --skip=5 | FileCheck %s --check-prefixes=CHECK,CHECK2
 
 CHECK: MallocFreeTracer: START
-CHECK: Unbalanced MALLOC[{{[0-9]+}}] [[PTR:0x[0-9a-f]+]] 4
+# Behavior of the format string "%p" is implementation defined. Account for the
+# implementation on Windows and Linux.
+CHECK: Unbalanced MALLOC[{{[0-9]+}}] [[PTR:(:?0x)?[0-9a-fA-F]+]] 4
 CHECK2-NEXT: {{ #0 0x[0-9a-f]+ in }}
 CHECK2-NEXT: {{ #1 0x[0-9a-f]+ in }}
 CHECK2-NEXT: {{ #2 0x[0-9a-f]+ in }}
 CHECK: MallocFreeTracer: STOP
 
 CHECK: MallocFreeTracer: START
 CHECK: Unbalanced FREE[{{[0-9]+}}] [[PTR]]
 CHECK2-NEXT: {{ #0 0x[0-9a-f]+ in }}
 CHECK2-NEXT: {{ #1 0x[0-9a-f]+ in }}
 CHECK2-NEXT: {{ #2 0x[0-9a-f]+ in }}
 CHECK: MallocFreeTracer: STOP