2019年7月15日 · This was deemed unacceptable, so pid_t was created and the implementation was allowed to define pid_t whichever way it prefers. Note that you are by no means obligated to use pid_t in your own code as long as you use a type that's large enough to store any pid ( intmax_t for example would work just fine).

2018年11月12日 · data types that ends with "_t", are usually a defined type variable in C and C++ as an unwritten law. according to that law, "pid_t" is a data type which is defined somewhere else but "int" a standard type; so to know the differences you need to know how "pid_t" is defined.

2015年8月29日 · In older Posix standards, pid_t was only defined in <sys/types.h>, but since Posix.1-2001 (Issue 7) it is also in <unistd.h>. However, in order to get definitions in Posix.1-2001, you must define an appropriate feature test macro before including any standard header file.

2009年12月17日 · In other words, uid_t and gid_t are unsigned 32-bit integers and pid_t is a signed 32-bit integer. This applies for both 32- and 64-bits. This applies for both 32- and 64-bits. I am not sure what they are on other architectures offhand as I don't have any available at the moment, but the definitive way is to compile a program which prints the ...

2013年12月12日 · With integer types lacking a matching format specifier as in the case of pid_t, yet with known sign-ness 1, cast to widest matching signed type and print.

2014年5月30日 · If I had to take a wild guess as to why pid_t is defined as __pid_t and not some int is because __pid_t is what Debian's or the Linux Kernel's developers decided to use for the process ID variable name in all of their library functions; therefore only '__pid_t' needs to be changed to change the integer size for a process ID.

2015年12月19日 · pid_t pid; pid = fork(); Now OS make two identical copies of address spaces, one for the parent and the other for the child. Both parent and child process start their execution right after the system call fork().

The type of the variable pid is pid_t. How pid_t itself is defined is dependant on the operating system. In Linux it's defined like this: typedef __pid_t pid_t; and __pid_t is eventually defined as an int. See GCC declarations: typedef __pid_t pid_t?

2012年10月20日 · I am getting this error: unknown type name 'pid_t'. I think Build is failing due to commenting of a header file: unistd.h. Since windows does not support unistd.h, i comment #include <unistd> and the only use of this header is pid_t so I am looking forward to add pid_t definition manually in Visual Studio based on this answer. any help?

2020年10月2日 · pid_t is not opaque. Zero and all negative values are explicitly exceptional (used e.g. by waitpid to represent particular classes of processes to wait for) and arguably 1 is exceptional too since the specialness of -1 prevents 1 from being a process group id you can use normally (traditionally, pid 1 is the init process).