[libFuzzer] [Tests] [NFC] Write output to files first before comparing with FileCheck

[george.karpenkov]

Summary

FileCheck is very good at making debugging difficult by hiding the original input.
A proper fix here would be to add an option to FileCheck to not do this,
but as a temporary solution using files seems to be the way to go.

[morehouse]

This makes the test more complex. What is the reason for this change?

[george.karpenkov]

Debugging those is very unpleasant otherwise. But probably it has to be solved on FileCheck level.

compiler-rt/test/fuzzer/reduce_inputs.test

 # Test -reduce_inputs=1
 
 RUN: rm -rf %t/C
+RUN: rm -f %t-shrink-simple.log %t-shrink-longer.log %t-shrink-redundant.log
 RUN: mkdir -p %t/C
+
 RUN: %cpp_compiler %S/ShrinkControlFlowSimpleTest.cpp -o %t-ShrinkControlFlowSimpleTest
 RUN: %cpp_compiler %S/ShrinkControlFlowTest.cpp -o %t-ShrinkControlFlowTest
-RUN: %run %t-ShrinkControlFlowSimpleTest  -exit_on_item=0eb8e4ed029b774d80f2b66408203801cb982a60   -runs=1000000 %t/C 2>&1 | FileCheck %s
+RUN: %run %t-ShrinkControlFlowSimpleTest  -exit_on_item=0eb8e4ed029b774d80f2b66408203801cb982a60   -runs=1000000 %t/C >%t-shrink-simple.log 2>&1 
+RUN: cat %t-shrink-simple.log | FileCheck %s
 CHECK: INFO: found item with checksum '0eb8e4ed029b774d80f2b66408203801cb982a60'
 
 # Test that reduce_inputs deletes redundant files in the corpus.
-RUN: %run %t-ShrinkControlFlowSimpleTest -runs=0 %t/C 2>&1 | FileCheck %s --check-prefix=COUNT
+RUN: %run %t-ShrinkControlFlowSimpleTest -runs=0 %t/C >%t-shrink-redundant.log 2>&1 
+RUN: cat %t-shrink-redundant.log | FileCheck %s --check-prefix=COUNT
 COUNT: seed corpus: files: 4
 
 # a bit longer test
-RUN: %run %t-ShrinkControlFlowTest  -exit_on_item=0eb8e4ed029b774d80f2b66408203801cb982a60  -seed=1 -runs=1000000  2>&1 | FileCheck %s
+RUN: %run %t-ShrinkControlFlowTest  -exit_on_item=0eb8e4ed029b774d80f2b66408203801cb982a60  -seed=1 -runs=1000000 >%t-shrink-longer.log 2>&1 
+RUN: cat %t-shrink-longer.log | FileCheck %s