[llvm-exegesis] Close file descriptors after use (#86584)

There are several insstances in the subprocess executor in llvm-exegesis
where we fail to close file descriptors after using them. This leaves
them open, which can cause issues later on if a third-party binary is
using the exegesis libraries and executing many blocks before exiting.
Leaving the descriptors open until process exit is also bad practice.
This patch fixes that by explicitly calling close() when we are done
with a specific file descriptor.

This patch fixes #86583.

Author: boomanaiden154

llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp

@@ -18,6 +18,7 @@
 #include "PerfHelper.h"
 #include "SubprocessMemory.h"
 #include "Target.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
@@ -283,6 +284,7 @@ class SubProcessFunctionExecutorImpl
                    SmallVectorImpl<int64_t> &CounterValues,
                    ArrayRef<const char *> ValidationCounters,
                    SmallVectorImpl<int64_t> &ValidationCounterValues) const {
+    auto WriteFDClose = make_scope_exit([WriteFD]() { close(WriteFD); });
     const ExegesisTarget &ET = State.getExegesisTarget();
     auto CounterOrError =
         ET.createCounter(CounterName, State, ValidationCounters, ChildPID);

llvm/tools/llvm-exegesis/lib/SubprocessMemory.cpp

@@ -8,6 +8,7 @@
 
 #include "SubprocessMemory.h"
 #include "Error.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
 #include <cerrno>
@@ -56,6 +57,8 @@ Error SubprocessMemory::initializeSubprocessMemory(pid_t ProcessID) {
     return make_error<Failure>(
         "Failed to create shared memory object for auxiliary memory: " +
         Twine(strerror(errno)));
+  auto AuxiliaryMemoryFDClose =
+      make_scope_exit([AuxiliaryMemoryFD]() { close(AuxiliaryMemoryFD); });
   if (ftruncate(AuxiliaryMemoryFD, AuxiliaryMemorySize) != 0) {
     return make_error<Failure>("Truncating the auxiliary memory failed: " +
                                Twine(strerror(errno)));
@@ -78,6 +81,8 @@ Error SubprocessMemory::addMemoryDefinition(
       return make_error<Failure>(
           "Failed to create shared memory object for memory definition: " +
           Twine(strerror(errno)));
+    auto SharedMemoryFDClose =
+        make_scope_exit([SharedMemoryFD]() { close(SharedMemoryFD); });
     if (ftruncate(SharedMemoryFD, MemVal.SizeBytes) != 0) {
       return make_error<Failure>("Truncating a memory definiton failed: " +
                                  Twine(strerror(errno)));