refactor(3p/nix): Apply clang-tidy's modernize-* fixes r/787

This applies the modernization fixes listed here:

https://clang.llvm.org/extra/clang-tidy/checks/list.html

The 'modernize-use-trailing-return-type' fix was excluded due to my
personal preference (more specifically, I think the 'auto' keyword is
misleading in that position).

2 files changed, 12 insertions, 11 deletions

diff --git a/third_party/nix/src/libmain/shared.cc b/third_party/nix/src/libmain/shared.cc
index f63fe9c11c..8ff7cebbee 100644
--- a/third_party/nix/src/libmain/shared.cc
+++ b/third_party/nix/src/libmain/shared.cc
@@ -2,14 +2,15 @@
 
 #include <algorithm>
 #include <cctype>
+#include <csignal>
 #include <cstdlib>
 #include <exception>
 #include <iostream>
 #include <mutex>
+#include <utility>
 
 #include <glog/logging.h>
 #include <openssl/crypto.h>
-#include <signal.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <unistd.h>
@@ -128,13 +129,13 @@ void initNix() {
   sigemptyset(&act.sa_mask);
   act.sa_handler = SIG_DFL;
   act.sa_flags = 0;
-  if (sigaction(SIGCHLD, &act, 0)) {
+  if (sigaction(SIGCHLD, &act, nullptr)) {
     throw SysError("resetting SIGCHLD");
   }
 
   /* Install a dummy SIGUSR1 handler for use with pthread_kill(). */
   act.sa_handler = sigHandler;
-  if (sigaction(SIGUSR1, &act, 0)) {
+  if (sigaction(SIGUSR1, &act, nullptr)) {
     throw SysError("handling SIGUSR1");
   }
 
@@ -159,7 +160,7 @@ void initNix() {
 
   /* Initialise the PRNG. */
   struct timeval tv;
-  gettimeofday(&tv, 0);
+  gettimeofday(&tv, nullptr);
   srandom(tv.tv_usec);
 
   /* On macOS, don't use the per-session TMPDIR (as set e.g. by
@@ -175,7 +176,7 @@ LegacyArgs::LegacyArgs(
     const std::string& programName,
     std::function<bool(Strings::iterator& arg, const Strings::iterator& end)>
         parseArg)
-    : MixCommonArgs(programName), parseArg(parseArg) {
+    : MixCommonArgs(programName), parseArg(std::move(parseArg)) {
   mkFlag()
       .longName("no-build-output")
       .shortName('Q')
@@ -395,6 +396,6 @@ PrintFreed::~PrintFreed() {
   }
 }
 
-Exit::~Exit() {}
+Exit::~Exit() = default;
 
 }  // namespace nix
diff --git a/third_party/nix/src/libmain/stack.cc b/third_party/nix/src/libmain/stack.cc
index 27c16f5d1f..87018b975c 100644
--- a/third_party/nix/src/libmain/stack.cc
+++ b/third_party/nix/src/libmain/stack.cc
@@ -1,8 +1,8 @@
+#include <csignal>
 #include <cstddef>
 #include <cstdlib>
 #include <cstring>
 
-#include <signal.h>
 #include <unistd.h>
 
 #include "types.hh"
@@ -14,7 +14,7 @@ static void sigsegvHandler(int signo, siginfo_t* info, void* ctx) {
      the stack pointer.  Unfortunately, getting the stack pointer is
      not portable. */
   bool haveSP = true;
-  char* sp = 0;
+  char* sp = nullptr;
 #if defined(__x86_64__) && defined(REG_RSP)
   sp = (char*)((ucontext_t*)ctx)->uc_mcontext.gregs[REG_RSP];
 #elif defined(REG_ESP)
@@ -40,7 +40,7 @@ static void sigsegvHandler(int signo, siginfo_t* info, void* ctx) {
   sigfillset(&act.sa_mask);
   act.sa_handler = SIG_DFL;
   act.sa_flags = 0;
-  if (sigaction(SIGSEGV, &act, 0)) {
+  if (sigaction(SIGSEGV, &act, nullptr)) {
     abort();
   }
 }
@@ -58,7 +58,7 @@ void detectStackOverflow() {
     throw Error("cannot allocate alternative stack");
   }
   stack.ss_flags = 0;
-  if (sigaltstack(&stack, 0) == -1) {
+  if (sigaltstack(&stack, nullptr) == -1) {
     throw SysError("cannot set alternative stack");
   }
 
@@ -66,7 +66,7 @@ void detectStackOverflow() {
   sigfillset(&act.sa_mask);
   act.sa_sigaction = sigsegvHandler;
   act.sa_flags = SA_SIGINFO | SA_ONSTACK;
-  if (sigaction(SIGSEGV, &act, 0)) {
+  if (sigaction(SIGSEGV, &act, nullptr)) {
     throw SysError("resetting SIGSEGV");
   }
 #endif