unix: factor out reusable procfs exepath impl

On Linux we read `/proc/self/exe` for the path to the executable.
Factor out a dedicated source file to make this implementation
available for use on other platforms that support it.

PR-URL: https://github.com/libuv/libuv/pull/1312
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

Makefile.am

@@ -377,6 +377,7 @@ libuv_la_SOURCES += src/unix/linux-core.c \
                     src/unix/linux-inotify.c \
                     src/unix/linux-syscalls.c \
                     src/unix/linux-syscalls.h \
+                    src/unix/procfs-exepath.c \
                     src/unix/proctitle.c \
                     src/unix/sysinfo-loadavg.c \
                     src/unix/sysinfo-memory.c

src/unix/linux-core.c

@@ -472,26 +472,6 @@ uint64_t uv__hrtime(uv_clocktype_t type) {
 }
 
 
-int uv_exepath(char* buffer, size_t* size) {
-  ssize_t n;
-
-  if (buffer == NULL || size == NULL || *size == 0)
-    return -EINVAL;
-
-  n = *size - 1;
-  if (n > 0)
-    n = readlink("/proc/self/exe", buffer, n);
-
-  if (n == -1)
-    return -errno;
-
-  buffer[n] = '\0';
-  *size = n;
-
-  return 0;
-}
-
-
 int uv_resident_set_memory(size_t* rss) {
   char buf[1024];
   const char* s;

src/unix/procfs-exepath.c

@@ -0,0 +1,45 @@
+/* Copyright libuv project contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "internal.h"
+
+#include <stddef.h>
+#include <unistd.h>
+
+int uv_exepath(char* buffer, size_t* size) {
+  ssize_t n;
+
+  if (buffer == NULL || size == NULL || *size == 0)
+    return -EINVAL;
+
+  n = *size - 1;
+  if (n > 0)
+    n = readlink("/proc/self/exe", buffer, n);
+
+  if (n == -1)
+    return -errno;
+
+  buffer[n] = '\0';
+  *size = n;
+
+  return 0;
+}

uv.gyp

@@ -237,6 +237,7 @@
             'src/unix/linux-inotify.c',
             'src/unix/linux-syscalls.c',
             'src/unix/linux-syscalls.h',
+            'src/unix/procfs-exepath.c',
             'src/unix/sysinfo-loadavg.c',
             'src/unix/sysinfo-memory.c',
           ],
@@ -253,6 +254,7 @@
             'src/unix/pthread-fixes.c',
             'src/unix/android-ifaddrs.c',
             'src/unix/pthread-barrier.c'
+            'src/unix/procfs-exepath.c',
             'src/unix/sysinfo-loadavg.c',
             'src/unix/sysinfo-memory.c',
           ],