3014. More noexcept issues with filesystem operations

Section: 31.12.13.5 [fs.op.copy.file], 31.12.13.7 [fs.op.create.directories], 31.12.13.32 [fs.op.remove.all] Status: C++20 Submitter: Tim Song Opened: 2017-08-23 Last modified: 2021-06-06

Priority: Not Prioritized

View all other issues in [fs.op.copy.file].

View all issues with C++20 status.

Discussion:

create_directories may need to create temporary paths, and remove_all may need to create temporary paths and/or directory_iterators. These operations may require a potentially throwing memory allocation.

Implementations of copy_file may wish to dynamically allocate the buffer used for copying when the underlying OS doesn't supply a copy API directly. This can happen indirectly, e.g., by using <fstream> facilities to perform the copying without supplying a custom buffer. Unless LWG wishes to prohibit using a dynamically allocated buffer in this manner, the noexcept should be removed.

[2017-11 Albuquerque Wednesday night issues processing]

Moved to Ready

[2018-3-17 Adopted in Jacksonville]

Proposed resolution:

This wording is relative to N4687.

1. Edit 31.12.4 [fs.filesystem.syn], header <filesystem> synopsis, as indicated:

   namespace std::filesystem {
   
     […]
   
     bool copy_file(const path& from, const path& to);
     bool copy_file(const path& from, const path& to, error_code& ec) noexcept;
     bool copy_file(const path& from, const path& to, copy_options option);
     bool copy_file(const path& from, const path& to, copy_options option,
                    error_code& ec) noexcept;
   
     […]
   
     bool create_directories(const path& p);
     bool create_directories(const path& p, error_code& ec) noexcept;
   
     […]
   
     uintmax_t remove_all(const path& p);
     uintmax_t remove_all(const path& p, error_code& ec) noexcept;
   
     […]
   }
   

2. Edit [fs.op.copy_file] as indicated:

   bool copy_file(const path& from, const path& to);
   bool copy_file(const path& from, const path& to, error_code& ec) noexcept;
   

   -1- Returns: […]

   -2- Throws: […]

   bool copy_file(const path& from, const path& to, copy_options options);
   bool copy_file(const path& from, const path& to, copy_options options,
                  error_code& ec) noexcept;
   

   -3- Requires: […]

   -4- Effects: […]

   -5- Returns: […]

   -6- Throws: […]

   -7- Complexity: […]

3. Edit [fs.op.create_directories] as indicated:

   bool create_directories(const path& p);
   bool create_directories(const path& p, error_code& ec) noexcept;
   

   -1- Effects: […]

   -2- Postconditions: […]

   -3- Returns: […]

   -4- Throws: […]

   -5- Complexity: […]

4. Edit [fs.op.remove_all] as indicated:

   uintmax_t remove_all(const path& p);
   uintmax_t remove_all(const path& p, error_code& ec) noexcept;
   

   -1- Effects: […]

   -2- Postconditions: […]

   -3- Returns: […]

   -4- Throws: […]