Difference between revisions of "VMS Python compatibility issues"
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| − | + | = File system = | |
| − | + | #Directories and files with the same name are allowed | |
| − | + | #Files have versioning, therefore two files with the same name might have different content | |
| − | + | #Shared stream I/O does not work | |
| − | + | #To guarantee the file content is on the disk the <code>fsync()</code> function must be used | |
| − | + | #Because files can be referenced using logical names the real file path may be different from the “path” used to open a file | |
| − | + | #Files has no access time attribute | |
| − | + | #Changing a files permissions also changes its modification time | |
| − | + | #Changing the content of a directory does not change the directory modification time. | |
| − | + | #Files have four rights bits (read, write, execute, and delete); Linux (UNIX) has only three (read, write, and execute) | |
| − | + | #The ‘.DIR’ extension is reserved | |
| − | + | #Non-blocking file IO is not supported by the OpenVMS CRTL | |
| − | + | #There are various known issues with symbolic link implementation | |
| − | + | #The symbol '$' is commonly used in file and directory names | |
| − | + | #On OpenVMS chmod(0) sets the user's default permissions as opposed to resetting permissions | |
| − | + | #To delete a directory the user has to have ‘delete’ permission for the directory | |
| − | + | #On OpenVMS <code>mkdir()</code> creates all intermediate directories (if required) | |
| − | + | = Process = | |
| − | + | #There are no Linux-like <code>fork()</code> and <code>spawn()</code> functions | |
| − | + | #Pipes are created via mailbox and are not totally compatible with UNIX pipes (compatibility issues) | |
| − | + | #If a child process has threads, each thread posts 'END-OF-PIPE' when the child completes/terminates | |
| − | + | #The functions <code>select()</code> and <code>poll()</code> work only with sockets | |
| − | + | #The function <code>siginterrupt()</code> is not supported | |
| − | + | #Numerous compatibility issues with signals | |
| − | + | #Interrupting I/O operations may cause the process to hang | |
| − | + | #There is no root user with zero UID | |
| − | + | #Processes do not handle recursion overflow cleanly | |
| − | + | = Sockets = | |
| − | + | #<code>AF_UNIX</code> has somewhat different meaning | |
| − | + | #Binding a socket to an empty address fails (wildcard resolved to multiple address) | |
| − | + | #<code>getpeername()</code> returns ‘0.0.0.0’ instead of an error | |
| − | # | + | #<code>socket.socket.sendall</code> does not work correctly (process may crash) |
| − | + | = Time = | |
| − | + | #<code>time_t</code> is unsigned | |
| − | + | #<code>strftime()</code> | |
| − | + | #*Does not support <code>%G</code> format | |
| − | + | #*Exhibits undefined behavior when format ends with <code>%</code> | |
| − | + | #*<code>%4Y</code> is padded with spaces | |
| − | + | = Miscellaneous = | |
| − | # | + | #There is no appropriate way to programmatically get all environment variables (logical names and/or symbols) |
| − | # | + | #The current OpenVMS port of sqlite3 does not support "OR ROLLBACK" |
| − | + | #<code>locale.strxfrm()</code> does not work as expected | |
| − | + | = Compiler = | |
| − | + | #<code>uint_ptr</code> is always 64-bit, <code>void*</code> is either 32-bit or 64-bit (depending on selected pointer size) | |
| − | + | #Compiler does not support relative include paths | |
| − | |||
---- | ---- | ||
| − | [[Category:VMS | + | [[Category:VMS Python]] |
Latest revision as of 07:50, 1 July 2021
File system
- Directories and files with the same name are allowed
- Files have versioning, therefore two files with the same name might have different content
- Shared stream I/O does not work
- To guarantee the file content is on the disk the
fsync()function must be used - Because files can be referenced using logical names the real file path may be different from the “path” used to open a file
- Files has no access time attribute
- Changing a files permissions also changes its modification time
- Changing the content of a directory does not change the directory modification time.
- Files have four rights bits (read, write, execute, and delete); Linux (UNIX) has only three (read, write, and execute)
- The ‘.DIR’ extension is reserved
- Non-blocking file IO is not supported by the OpenVMS CRTL
- There are various known issues with symbolic link implementation
- The symbol '$' is commonly used in file and directory names
- On OpenVMS chmod(0) sets the user's default permissions as opposed to resetting permissions
- To delete a directory the user has to have ‘delete’ permission for the directory
- On OpenVMS
mkdir()creates all intermediate directories (if required)
Process
- There are no Linux-like
fork()andspawn()functions - Pipes are created via mailbox and are not totally compatible with UNIX pipes (compatibility issues)
- If a child process has threads, each thread posts 'END-OF-PIPE' when the child completes/terminates
- The functions
select()andpoll()work only with sockets - The function
siginterrupt()is not supported - Numerous compatibility issues with signals
- Interrupting I/O operations may cause the process to hang
- There is no root user with zero UID
- Processes do not handle recursion overflow cleanly
Sockets
AF_UNIXhas somewhat different meaning- Binding a socket to an empty address fails (wildcard resolved to multiple address)
getpeername()returns ‘0.0.0.0’ instead of an errorsocket.socket.sendalldoes not work correctly (process may crash)
Time
time_tis unsignedstrftime()- Does not support
%Gformat - Exhibits undefined behavior when format ends with
% %4Yis padded with spaces
- Does not support
Miscellaneous
- There is no appropriate way to programmatically get all environment variables (logical names and/or symbols)
- The current OpenVMS port of sqlite3 does not support "OR ROLLBACK"
locale.strxfrm()does not work as expected
Compiler
uint_ptris always 64-bit,void*is either 32-bit or 64-bit (depending on selected pointer size)- Compiler does not support relative include paths
