- pass optional delegate to rt_configOption to allow processing each …

…found option

- use rt_configOption from gc.config

src/gc/config.d

@@ -31,34 +31,26 @@ struct Config
     size_t maxPoolSize = 64; // maximum pool size (MB)
     size_t incPoolSize = 3;  // pool size increment (MB)
 
-    bool initialize(...) // avoid inlining
+    bool initialize() @nogc
     {
-        foreach (a; rt_options)
-        {
-            if(a.length >= 6 && a[0..6] == "gcopt=")
-                if (!parseOptions(a[6 .. $]))
-                    return false;
-        }
-        if(rt_envvars_enabled)
-        {
-            auto p = getenv("DRT_GCOPT");
-            if (p)
-                if (!parseOptions(p[0 .. strlen(p)]))
-                    return false;
-        }
-        if(rt_cmdline_enabled)
+        import core.internal.traits : externDFunc;
+
+        alias rt_configCallBack = string delegate(string) @nogc nothrow;
+        alias fn_configOption = string function(string opt, scope rt_configCallBack dg, bool reverse) @nogc nothrow;
+
+        alias rt_configOption = externDFunc!("rt.config.rt_configOption", fn_configOption);
+
+        string parse(string opt) @nogc nothrow
         {
-            foreach (a; rt_args)
-            {
-                if(a.length >= 12 && a[0..12] == "--DRT-gcopt=")
-                    if (!parseOptions(a[12 .. $]))
-                        return false;
-            }
+            if (!parseOptions(opt))
+                return "err";
+            return null; // continue processing
         }
-        return true;
+        string s = rt_configOption("gcopt", &parse, true);
+        return s is null;
     }
 
-    void help() @nogc
+    void help() @nogc nothrow
     {
         string s = "GC options are specified as white space separated assignments:
     disable:0|1    - start disabled (%d)
@@ -75,7 +67,7 @@ struct Config
                cast(long)minPoolSize, cast(long)maxPoolSize, cast(long)incPoolSize);
     }
 
-    bool parseOptions(const(char)[] opt) @nogc
+    bool parseOptions(const(char)[] opt) @nogc nothrow
     {
         size_t p = 0;
         while(p < opt.length)

src/rt/config.d

@@ -58,27 +58,54 @@ import core.stdc.string : strlen;
 
 extern extern(C) string[] rt_args() @nogc nothrow;
 
+alias rt_configCallBack = string delegate(string) @nogc nothrow;
+
 /**
 * get a druntime config option using standard configuration options
 *      opt             name of the option to retreive
+*      dg              if non-null, passes the option through this
+*                      delegate and only returns its return value if non-null
+*      reverse         reverse the default processing order cmdline/envvar/rt_options
+*                      to allow overwriting settings in the delegate with values
+*                      from higher priority
 *
 * returns the options' value if
 *  - set on the command line as "--DRT-<opt>=value" (rt_cmdline_enabled enabled)
 *  - the environment variable "DRT_<OPT>" is set (rt_envvars_enabled enabled)
 *  - rt_options[] contains an entry "<opt>=value"
 *  - null otherwise
 */
-string rt_configOption(string opt) @nogc nothrow
+string rt_configOption(string opt, scope rt_configCallBack dg = null, bool reverse = false) @nogc nothrow
+{
+    if (!dg)
+        dg = (string s) => s;
+
+    if (string s = (reverse ? rt_linkOption(opt, dg) : rt_cmdlineOption(opt, dg)))
+        return s;
+    if (string s = rt_envvarsOption(opt, dg))
+        return s;
+    if (string s = (reverse ? rt_cmdlineOption(opt, dg) : rt_linkOption(opt, dg)))
+        return s;
+    return null;
+}
+
+string rt_cmdlineOption(string opt, rt_configCallBack dg) @nogc nothrow
 {
     if(rt_cmdline_enabled!())
     {
         foreach (a; rt_args)
         {
             if (a.length >= opt.length + 7 && a[0..6] == "--DRT-" &&
                 a[6 .. 6 + opt.length] == opt && a[6 + opt.length] == '=')
-                return a[7 + opt.length .. $];
+                if (string s = dg(a[7 + opt.length .. $]))
+                    return s;
         }
     }
+    return null;
+}
+
+string rt_envvarsOption(string opt, rt_configCallBack dg) @nogc nothrow
+{
     if(rt_envvars_enabled!())
     {
         if (opt.length >= 32)
@@ -92,13 +119,19 @@ string rt_configOption(string opt) @nogc nothrow
 
         auto p = getenv(var.ptr);
         if (p)
-            return cast(string) p[0 .. strlen(p)];
+            if (string s = dg(cast(string) p[0 .. strlen(p)]))
+                return s;
     }
+    return null;
+}
+
+string rt_linkOption(string opt, rt_configCallBack dg) @nogc nothrow
+{
     foreach (a; rt_options!())
     {
         if(a.length > opt.length && a[0..opt.length] == opt && a[opt.length] == '=')
-            return a[opt.length + 1 .. $];
+            if (string s = dg(a[opt.length + 1 .. $]))
+                return s;
     }
     return null;
 }
-