include/llvm/Support/Process.h

   1 //===- llvm/Support/Process.h -----------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 /// \file
   9 ///
  10 /// Provides a library for accessing information about this process and other
  11 /// processes on the operating system. Also provides means of spawning
  12 /// subprocess for commands. The design of this library is modeled after the
  13 /// proposed design of the Boost.Process library, and is design specifically to
  14 /// follow the style of standard libraries and potentially become a proposal
  15 /// for a standard library.
  16 ///
  17 /// This file declares the llvm::sys::Process class which contains a collection
  18 /// of legacy static interfaces for extracting various information about the
  19 /// current process. The goal is to migrate users of this API over to the new
  20 /// interfaces.
  21 ///
  22 //===----------------------------------------------------------------------===//
  23
  24 #ifndef LLVM_SUPPORT_PROCESS_H
  25 #define LLVM_SUPPORT_PROCESS_H
  26
  27 #include "llvm/ADT/Optional.h"
  28 #include "llvm/Support/Allocator.h"
  29 #include "llvm/Support/Chrono.h"
  30 #include "llvm/Support/DataTypes.h"
  31 #include "llvm/Support/Error.h"
  32 #include <system_error>
  33
  34 namespace llvm {
  35 template <typename T> class ArrayRef;
  36 class StringRef;
  37
  38 namespace sys {
  39
  40
  41 /// A collection of legacy interfaces for querying information about the
  42 /// current executing process.
  43 class Process {
  44 public:
  45   /// Get the process's page size.
  46   /// This may fail if the underlying syscall returns an error. In most cases,
  47   /// page size information is used for optimization, and this error can be
  48   /// safely discarded by calling consumeError, and an estimated page size
  49   /// substituted instead.
  50   static Expected<unsigned> getPageSize();
  51
  52   /// Get the process's estimated page size.
  53   /// This function always succeeds, but if the underlying syscall to determine
  54   /// the page size fails then this will silently return an estimated page size.
  55   /// The estimated page size is guaranteed to be a power of 2.
  56   static unsigned getPageSizeEstimate() {
  57     if (auto PageSize = getPageSize())
  58       return *PageSize;
  59     else {
  60       consumeError(PageSize.takeError());
  61       return 4096;
  62     }
  63   }
  64
  65   /// Return process memory usage.
  66   /// This static function will return the total amount of memory allocated
  67   /// by the process. This only counts the memory allocated via the malloc,
  68   /// calloc and realloc functions and includes any "free" holes in the
  69   /// allocated space.
  70   static size_t GetMallocUsage();
  71
  72   /// This static function will set \p user_time to the amount of CPU time
  73   /// spent in user (non-kernel) mode and \p sys_time to the amount of CPU
  74   /// time spent in system (kernel) mode.  If the operating system does not
  75   /// support collection of these metrics, a zero duration will be for both
  76   /// values.
  77   /// \param elapsed Returns the system_clock::now() giving current time
  78   /// \param user_time Returns the current amount of user time for the process
  79   /// \param sys_time Returns the current amount of system time for the process
  80   static void GetTimeUsage(TimePoint<> &elapsed,
  81                            std::chrono::nanoseconds &user_time,
  82                            std::chrono::nanoseconds &sys_time);
  83
  84   /// This function makes the necessary calls to the operating system to
  85   /// prevent core files or any other kind of large memory dumps that can
  86   /// occur when a program fails.
  87   /// Prevent core file generation.
  88   static void PreventCoreFiles();
  89
  90   /// true if PreventCoreFiles has been called, false otherwise.
  91   static bool AreCoreFilesPrevented();
  92
  93   // This function returns the environment variable \arg name's value as a UTF-8
  94   // string. \arg Name is assumed to be in UTF-8 encoding too.
  95   static Optional<std::string> GetEnv(StringRef name);
  96
  97   /// This function searches for an existing file in the list of directories
  98   /// in a PATH like environment variable, and returns the first file found,
  99   /// according to the order of the entries in the PATH like environment
 100   /// variable.  If an ignore list is specified, then any folder which is in
 101   /// the PATH like environment variable but is also in IgnoreList is not
 102   /// considered.
 103   static Optional<std::string> FindInEnvPath(StringRef EnvName,
 104                                              StringRef FileName,
 105                                              ArrayRef<std::string> IgnoreList);
 106
 107   static Optional<std::string> FindInEnvPath(StringRef EnvName,
 108                                              StringRef FileName);
 109
 110   // This functions ensures that the standard file descriptors (input, output,
 111   // and error) are properly mapped to a file descriptor before we use any of
 112   // them.  This should only be called by standalone programs, library
 113   // components should not call this.
 114   static std::error_code FixupStandardFileDescriptors();
 115
 116   // This function safely closes a file descriptor.  It is not safe to retry
 117   // close(2) when it returns with errno equivalent to EINTR; this is because
 118   // *nixen cannot agree if the file descriptor is, in fact, closed when this
 119   // occurs.
 120   //
 121   // N.B. Some operating systems, due to thread cancellation, cannot properly
 122   // guarantee that it will or will not be closed one way or the other!
 123   static std::error_code SafelyCloseFileDescriptor(int FD);
 124
 125   /// This function determines if the standard input is connected directly
 126   /// to a user's input (keyboard probably), rather than coming from a file
 127   /// or pipe.
 128   static bool StandardInIsUserInput();
 129
 130   /// This function determines if the standard output is connected to a
 131   /// "tty" or "console" window. That is, the output would be displayed to
 132   /// the user rather than being put on a pipe or stored in a file.
 133   static bool StandardOutIsDisplayed();
 134
 135   /// This function determines if the standard error is connected to a
 136   /// "tty" or "console" window. That is, the output would be displayed to
 137   /// the user rather than being put on a pipe or stored in a file.
 138   static bool StandardErrIsDisplayed();
 139
 140   /// This function determines if the given file descriptor is connected to
 141   /// a "tty" or "console" window. That is, the output would be displayed to
 142   /// the user rather than being put on a pipe or stored in a file.
 143   static bool FileDescriptorIsDisplayed(int fd);
 144
 145   /// This function determines if the given file descriptor is displayd and
 146   /// supports colors.
 147   static bool FileDescriptorHasColors(int fd);
 148
 149   /// This function determines the number of columns in the window
 150   /// if standard output is connected to a "tty" or "console"
 151   /// window. If standard output is not connected to a tty or
 152   /// console, or if the number of columns cannot be determined,
 153   /// this routine returns zero.
 154   static unsigned StandardOutColumns();
 155
 156   /// This function determines the number of columns in the window
 157   /// if standard error is connected to a "tty" or "console"
 158   /// window. If standard error is not connected to a tty or
 159   /// console, or if the number of columns cannot be determined,
 160   /// this routine returns zero.
 161   static unsigned StandardErrColumns();
 162
 163   /// This function determines whether the terminal connected to standard
 164   /// output supports colors. If standard output is not connected to a
 165   /// terminal, this function returns false.
 166   static bool StandardOutHasColors();
 167
 168   /// This function determines whether the terminal connected to standard
 169   /// error supports colors. If standard error is not connected to a
 170   /// terminal, this function returns false.
 171   static bool StandardErrHasColors();
 172
 173   /// Enables or disables whether ANSI escape sequences are used to output
 174   /// colors. This only has an effect on Windows.
 175   /// Note: Setting this option is not thread-safe and should only be done
 176   /// during initialization.
 177   static void UseANSIEscapeCodes(bool enable);
 178
 179   /// Whether changing colors requires the output to be flushed.
 180   /// This is needed on systems that don't support escape sequences for
 181   /// changing colors.
 182   static bool ColorNeedsFlush();
 183
 184   /// This function returns the colorcode escape sequences.
 185   /// If ColorNeedsFlush() is true then this function will change the colors
 186   /// and return an empty escape sequence. In that case it is the
 187   /// responsibility of the client to flush the output stream prior to
 188   /// calling this function.
 189   static const char *OutputColor(char c, bool bold, bool bg);
 190
 191   /// Same as OutputColor, but only enables the bold attribute.
 192   static const char *OutputBold(bool bg);
 193
 194   /// This function returns the escape sequence to reverse forground and
 195   /// background colors.
 196   static const char *OutputReverse();
 197
 198   /// Resets the terminals colors, or returns an escape sequence to do so.
 199   static const char *ResetColor();
 200
 201   /// Get the result of a process wide random number generator. The
 202   /// generator will be automatically seeded in non-deterministic fashion.
 203   static unsigned GetRandomNumber();
 204 };
 205
 206 }
 207 }
 208
 209 #endif