read bootstrap file relative to exe path

src/main.cc

@@ -6,6 +6,8 @@
 #include <fcntl.h>
 #include <unistd.h>
 
+#define SHARE_BOOTSTRAP "/share/svi/bootstrap.rb"
+
 VALUE svi_ruby_protect_eval_string_rescue(VALUE exception, VALUE exception_object)
 {
     *(bool *)exception = true;
@@ -57,14 +59,47 @@ static char * read_file(const char * filename)
     }
 }
 
+std::string get_exe_path()
+{
+    pid_t pid = getpid();
+    char proc_path[25];
+    sprintf(proc_path, "/proc/%d/exe", pid);
+    char exe_path[100];
+    ssize_t n = readlink(proc_path, exe_path, sizeof(exe_path));
+    if ((n > 0) && (n < (ssize_t)sizeof(exe_path)))
+    {
+        return exe_path;
+    }
+    return "";
+}
+
+const char * read_bootstrap_file()
+{
+    auto exe_path = get_exe_path();
+    size_t index = exe_path.rfind('/');
+    if ((index != std::string::npos) && (index > 0u))
+    {
+        index = exe_path.rfind('/', index - 1u);
+        if (index != std::string::npos)
+        {
+            std::string path = std::string(exe_path, 0u, index) + SHARE_BOOTSTRAP;
+            char * bootstrap = read_file(path.c_str());
+            if (bootstrap != nullptr)
+            {
+                return bootstrap;
+            }
+        }
+    }
+    return read_file(SHARE_DIR SHARE_BOOTSTRAP);
+}
+
 int main(int argc, char * argv[])
 {
-    static const char * ruby_startup_file = SHARE_DIR "/svi.rb";
     bool exception = false;
-    char * ruby_startup = read_file(ruby_startup_file);
+    const char * ruby_startup = read_bootstrap_file();
     if (ruby_startup == nullptr)
     {
-        fprintf(stderr, "Error opening %s\n", ruby_startup_file);
+        fprintf(stderr, "Could not read Ruby startup file\n");
         return 1;
     }
     {