fixes #9965

compiler/options.nim

@@ -253,6 +253,80 @@ template depConfigFields*(fn) {.dirty.} =
   fn(globalOptions)
   fn(selectedGC)
 
+proc mergeConfigs*(dest, src: ConfigRef) =
+  template merge[T: enum](a, b: T) =
+    a = b
+  template merge[T](a, b: set[T]) =
+    a = a + b
+  template merge(a, b: int) =
+    inc a, b
+  template merge[T](a, b: seq[T]) =
+    for bb in b: a.add b
+  template merge(a, b: string) =
+    a = b
+  template merge[T: AbsoluteFile|AbsoluteDir](a, b: T) =
+    if a.isEmpty and not b.isEmpty: a = b
+
+  template merge[T](a, b: HashSet[T]) =
+    for bb in b: a.incl b
+  template merge(a, b: StringTableRef) =
+    for k, v in b: a[k] = v
+  template merge[T: object](a, b: T) =
+    a = b
+
+  template m(field) =
+    merge(dest.field, src.field)
+
+  m target
+  m options
+  m globalOptions
+  m cmd
+  m selectedGC
+  m verbosity
+  m numberOfProcessors
+  m evalExpr
+  m symbolFiles
+  m cppDefines
+  m headerFile
+  m features
+  m arguments
+  m ideCmd
+  m cCompiler
+  m enableNotes
+  m disableNotes
+  m foreignPackageNotes
+  m notes
+  m errorCounter
+  m hintCounter
+  m warnCounter
+  m errorMax
+  m configVars
+  m symbols
+  m searchPaths
+  m lazyPaths
+  m outFile
+  m prefixDir
+  m libpath
+  m nimcacheDir
+  m dllOverrides
+  m moduleOverrides
+  m command
+  m commandArgs
+  m implicitImports
+  m implicitIncludes
+  m docSeeSrcUrl
+  m cIncludes
+  m cLibs
+  m cLinkedLibs
+  m externalToLink
+  m linkOptionsCmd
+  m compileOptionsCmd
+  m linkOptions
+  m compileOptions
+  m ccompilerpath
+  m toCompile
+  m cppCustomNamespace
+
 const oldExperimentalFeatures* = {implicitDeref, dotOperators, callOperator, parallel}
 
 const