Auto merge of #2974 - SteveLauC:dirname-basename, r=JohnTitor

add dirname and basename

This PR adds `dirname(3)` and `basename(3)` on the following platforms:
* Linux with glibc
* Linux with musl
* Android
* FreeBSD
* DragonFlyBSD
* NetBSD
* OpenBSD
* Apple platforms

I tested this PR on my host machine (Linux with glibc), and got the following error:
```
RUNNING ALL TESTS
bad basename function pointer: rust: 140093945892128 (0x7f6a29e14d20) != c 140093945544944 (0x7f6a29dc00f0)
thread 'main' panicked at 'some tests failed', /home/steve/Documents/workspace/libc/target/debug/build/libc-test-592f01d15ee93e7a/out/main.rs:12:21
stack backtrace:
   0: std::panicking::begin_panic
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:616:12
   1: main::main
             at /home/steve/Documents/workspace/libc/target/debug/build/libc-test-592f01d15ee93e7a/out/main.rs:12:21
   2: core::ops::function::FnOnce::call_once
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/ops/function.rs:248:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
error: test failed, to rerun pass '--test main'
```
The reason for this error probably is that there are two `basename(3)` on Linux with glibc, the  POSIX version and the GNU version, and they clash with each other. In C, if one `#include <libgen.h>`, then the POSIX version will be available; If one ` #define _GNU_SOURCE` and `#include <string.h>`, then the GNU one will be used.

Can we distinguish them in `libc`?

Author: bors

libc-test/build.rs

@@ -204,6 +204,7 @@ fn test_apple(target: &str) {
         "iconv.h",
         "ifaddrs.h",
         "langinfo.h",
+        "libgen.h",
         "libproc.h",
         "limits.h",
         "locale.h",
@@ -420,6 +421,7 @@ fn test_openbsd(target: &str) {
         "errno.h",
         "execinfo.h",
         "fcntl.h",
+        "libgen.h",
         "limits.h",
         "link.h",
         "locale.h",
@@ -995,6 +997,7 @@ fn test_netbsd(target: &str) {
         "elf.h",
         "errno.h",
         "fcntl.h",
+        "libgen.h",
         "limits.h",
         "link.h",
         "locale.h",
@@ -1209,6 +1212,7 @@ fn test_dragonflybsd(target: &str) {
         "ifaddrs.h",
         "kvm.h",
         "langinfo.h",
+        "libgen.h",
         "limits.h",
         "link.h",
         "locale.h",
@@ -1508,6 +1512,7 @@ fn test_android(target: &str) {
                "fcntl.h",
                "grp.h",
                "ifaddrs.h",
+               "libgen.h",
                "limits.h",
                "link.h",
                "locale.h",
@@ -1869,6 +1874,7 @@ fn test_freebsd(target: &str) {
                 "iconv.h",
                 "ifaddrs.h",
                 "langinfo.h",
+                "libgen.h",
                 "libutil.h",
                 "limits.h",
                 "link.h",
@@ -2774,6 +2780,7 @@ fn test_linux(target: &str) {
                "iconv.h",
                "ifaddrs.h",
                "langinfo.h",
+               "libgen.h",
                "limits.h",
                "link.h",
                "locale.h",
@@ -3413,6 +3420,22 @@ fn test_linux(target: &str) {
             // it can't be changed from struct.
             "pthread_sigqueue" => true,
 
+            // There are two versions of basename(3) on Linux with glibc, see
+            //
+            // https://man7.org/linux/man-pages/man3/basename.3.html
+            //
+            // If libgen.h is included, then the POSIX version will be available;
+            // If _GNU_SOURCE is defined and string.h is included, then the GNU one
+            // will be used.
+            //
+            // libc exposes both of them, providing a prefix to differentiate between
+            // them.
+            //
+            // Because the name with prefix is not a valid symbol in C, we have to
+            // skip the tests.
+            "posix_basename" if gnu => true,
+            "gnu_basename" if gnu => true,
+
             _ => false,
         }
     });

libc-test/semver/android.txt

@@ -3548,3 +3548,5 @@ winsize
 wmemchr
 write
 writev
+dirname
+basename

libc-test/semver/apple.txt

@@ -2227,3 +2227,5 @@ wait4
 waitid
 xsw_usage
 xucred
+dirname
+basename

libc-test/semver/dragonfly.txt

@@ -1546,3 +1546,5 @@ wait4
 waitid
 xucred
 eaccess
+dirname
+basename

libc-test/semver/freebsd.txt

@@ -1925,4 +1925,6 @@ wait4
 waitid
 xallocx
 xucred
-eaccess
+eaccess
+dirname
+basename

libc-test/semver/linux-gnu.txt

@@ -657,4 +657,7 @@ eaccess
 asctime_r
 ctime_r
 strftime
-strptime
+strptime
+dirname
+posix_basename
+gnu_basename

libc-test/semver/linux-musl.txt

@@ -52,4 +52,6 @@ euidaccess
 eaccess
 asctime_r
 strftime
-strptime
+strptime
+dirname
+basename

libc-test/semver/netbsd.txt

@@ -1533,3 +1533,5 @@ uucred
 vm_size_t
 wait4
 waitid
+dirname
+basename

libc-test/semver/openbsd.txt

@@ -1231,3 +1231,5 @@ utmp
 utrace
 wait4
 xucred
+dirname
+basename

src/unix/bsd/apple/mod.rs

@@ -5870,6 +5870,9 @@ extern "C" {
 
     pub fn malloc_size(ptr: *const ::c_void) -> ::size_t;
     pub fn malloc_good_size(size: ::size_t) -> ::size_t;
+
+    pub fn dirname(path: *mut ::c_char) -> *mut ::c_char;
+    pub fn basename(path: *mut ::c_char) -> *mut ::c_char;
 }
 
 pub unsafe fn mach_task_self() -> ::mach_port_t {