[tools] Fix not utility to work on iOS (#73)

* [tools] Fix not utility to work on iOS

This addresses issue #77137. The implementation uses posix_spawn on iOS but
std::system elsewhere.

Author: tarunprabhu

tools/CMakeLists.txt

@@ -40,12 +40,4 @@ else()
   llvm_add_host_executable(build-timeit timeit timeit.c)
 endif()
 
-# FIXME: the iOS buildbots can't build this since it uses `std::system`, but
-# since we don't support Fortram on the iOS bots and this utility is only used
-# by Fortran tests, it effectively "reverts to green", without entirely
-# reverting the patch.
-#
-# See: https://github.com/llvm/llvm-project/issues/77137
-if(TEST_SUITE_FORTRAN)
-  add_executable(not ${CMAKE_CURRENT_SOURCE_DIR}/not.cpp)
-endif()
+add_executable(not ${CMAKE_CURRENT_SOURCE_DIR}/not.cpp)

tools/not.cpp

@@ -24,7 +24,13 @@
 #include <windows.h>
 #endif
 
-int main(int argc, const char **argv) {
+#ifdef __APPLE__
+#include <spawn.h>
+#include <sys/wait.h>
+#include <TargetConditionals.h>
+#endif
+
+int main(int argc, char* const* argv) {
   bool expectCrash = false;
 
   ++argv;
@@ -49,13 +55,21 @@ int main(int argc, const char **argv) {
   if (argc == 0)
     return 1;
 
+  int result;
+#if !defined(TARGET_OS_IPHONE)
   std::stringstream ss;
   ss << argv[0];
   for (int i = 1; i < argc; ++i)
     ss << " " << argv[i];
   std::string cmd = ss.str();
-
-  int result = std::system(cmd.c_str());
+  result = std::system(cmd.c_str());
+#else
+  pid_t pid;
+  if (posix_spawn(&pid, argv[0], NULL, NULL, argv, NULL))
+    return EXIT_FAILURE;
+  if (waitpid(pid, &result, WUNTRACED | WCONTINUED) == -1)
+    return EXIT_FAILURE;
+#endif
   int retcode = 0;
   int signal = 0;