diff --git a/core/Dynamic.carp b/core/Dynamic.carp
index e62b214ab..ff72b7efd 100644
--- a/core/Dynamic.carp
+++ b/core/Dynamic.carp
@@ -95,10 +95,10 @@ integers [`imod`](#imod).")
 ;; The following functions are not put into a module for now:
 
 (defndynamic add-cflag [flag]
-  (eval (list 'Project.config "cflag" flag)))
+  (Project.config "cflag" (cons flag (Project.get-config "cflag"))))
 
 (defndynamic add-lib [lib]
-  (eval (list 'Project.config "libflag" lib)))
+  (Project.config "libflag" (cons lib (Project.get-config "libflag"))))
 
 (defndynamic pkg-config [pkg flags]
   (Dynamic.String.concat (Dynamic.append
diff --git a/core/Project.carp b/core/Project.carp
index 8c465d14a..978089b39 100644
--- a/core/Project.carp
+++ b/core/Project.carp
@@ -13,3 +13,13 @@
 Example usage: `(save-docs Int Float String)`")
 (defmacro save-docs [:rest modules]
   (eval (list 'save-docs-ex (list quote (collect-into modules array)) [])))
+
+(defmodule Project
+  (hidden append-flag)
+  (defndynamic append-flag [flag-set flag]
+    (Project.config flag-set (cons flag (Project.get-config flag-set))))
+
+  (defmacro append-cflag [flag] (Project.append-flag "cflag" flag))
+  (defmacro append-libflag [flag] (Project.append-flag "libflag" flag))
+  (defmacro append-pkgflag [flag] (Project.append-flag "pkgconfigflag" flag))
+)
diff --git a/core/SDL_mixer.carp b/core/SDL_mixer.carp
index cf139c9f8..d519e3ef6 100644
--- a/core/SDL_mixer.carp
+++ b/core/SDL_mixer.carp
@@ -1,6 +1,8 @@
 (system-include "SDL2/SDL_mixer.h")
 (add-pkg "SDL2_mixer")
-(Project.config "cflag" "-Wno-incompatible-pointer-types-discards-qualifiers")
+(Project.config "cflag"
+  (cons "-Wno-incompatible-pointer-types-discards-qualifiers"
+        (Project.get-config "cflag")))
 
 (register-type Mix_Chunk)
 (register-type Mix_Music)
diff --git a/core/SDL_ttf.carp b/core/SDL_ttf.carp
index dc46b2388..0ef1439af 100644
--- a/core/SDL_ttf.carp
+++ b/core/SDL_ttf.carp
@@ -1,6 +1,8 @@
 (system-include "SDL2/SDL_ttf.h")
 (add-pkg "SDL2_ttf")
-(Project.config "cflag" "-Wno-incompatible-pointer-types-discards-qualifiers")
+(Project.config "cflag"
+  (cons "-Wno-incompatible-pointer-types-discards-qualifiers"
+        (Project.get-config "cflag")))
 
 (register-type TTF_Font)
 
diff --git a/scripts/carp.sh b/scripts/carp.sh
index 6e90cf4a9..dcedc1f1c 100755
--- a/scripts/carp.sh
+++ b/scripts/carp.sh
@@ -10,4 +10,6 @@ then
     CARP="$CARP $BUILD_OPTS --"
 fi
 export CARP_DIR=`pwd`
-$CARP $CARP_OPTS "$@"
+# TODO: Temporary band-aid to make different versions of clang run tests OK when supported flag sets differ
+EVAL='(Project.config "cflag" (cons "-Wno-unknown-warning-option" (Project.get-config "cflag")))'
+$CARP --eval-preload "\'$EVAL\'" $CARP_OPTS "$@"
diff --git a/src/Obj.hs b/src/Obj.hs
index 1372fbfa6..9eba9e0de 100644
--- a/src/Obj.hs
+++ b/src/Obj.hs
@@ -218,6 +218,10 @@ isBool :: XObj -> Bool
 isBool (XObj (Bol _) _ _) = True
 isBool _ = False
 
+isStr :: XObj -> Bool
+isStr (XObj (Str _) _ _) = True
+isStr _ = False
+
 isExternalFunction :: XObj -> Bool
 isExternalFunction (XObj (Lst (XObj (External _) _ _ : _)) _ _) = True
 isExternalFunction _ = False
diff --git a/src/ProjectConfig.hs b/src/ProjectConfig.hs
index 473c4c811..ebeff9efd 100644
--- a/src/ProjectConfig.hs
+++ b/src/ProjectConfig.hs
@@ -1,9 +1,17 @@
 -- | Defines a frontend for manipulating Project level data.
 module ProjectConfig (projectKeyMap) where
 
+import Data.Either (rights)
 import Info
 import qualified Map
 import Obj
+    ( XObj(XObj),
+      Obj(Str, Lst, Bol),
+      unwrapStringXObj,
+      wrapString,
+      wrapList,
+      wrapArray,
+      isStr )
 import Project
 import Util
 
@@ -46,24 +54,15 @@ projectGetPreproc proj =
 -- | Get the project's C compiler flags.
 projectGetCFlags :: ProjectGetter
 projectGetCFlags proj =
-  let fs = projectPreproc proj
+  let fs = projectCFlags proj
    in wrapList (map wrapString fs)
 
 -- | Set the project's C compiler flags
---
--- NOTE: This retains existing behavior in which one can only add one flag at
--- a time and the flags are append only. A slightly more functional interface
--- would take a list of flags as arguments; e.g. to add *one* flag:
---
---   (Project.config "cflags" (cons "-my-flag" (Project.get-config "cflags")))
---
---   or to wipe the flags whole-cloth (e.g. for a different target)
---
---   (Project.config "cflags" ("-my" "-new" "-flags"))
---
---   likewise for flag removal etc.
 projectSetCFlags :: ProjectSetter
-projectSetCFlags proj (XObj (Str f) _ _) = Right (proj {projectCFlags = addIfNotPresent f (projectCFlags proj)})
+projectSetCFlags proj (XObj (Lst flags) _ _) =
+  if not $ all isStr flags
+    then Left "can't use a non-string as a C compiler flag"
+    else Right proj {projectCFlags = rights $ map unwrapStringXObj flags}
 projectSetCFlags _ _ = Left "can't use a non-string as a C compiler flag"
 
 -- | Get the project's C compiler library flags.
@@ -73,20 +72,11 @@ projectGetLibFlags proj =
    in wrapList (map wrapString ls)
 
 -- | Set the project's C compiler library flags
---
--- NOTE: This retains existing behavior in which one can only add one flag at
--- a time and the flags are append only. A slightly more functional interface
--- would take a list of flags as arguments; e.g. to add *one* flag:
---
---   (Project.config "libflags" (cons "-lmylib" (Project.get-config "libflags")))
---
---   or to wipe the flags whole-cloth (e.g. for a different target)
---
---   (Project.config "libflags" ("-lmy" "-lnew" "-llibflags"))
---
---   likewise for flag removal etc.
 projectSetLibFlags :: ProjectSetter
-projectSetLibFlags proj (XObj (Str flag) _ _) = Right (proj {projectLibFlags = addIfNotPresent flag (projectLibFlags proj)})
+projectSetLibFlags proj (XObj (Lst flags) _ _) =
+  if not $ all isStr flags
+    then Left "can't use a non-string as a C compiler library flag"
+    else Right proj {projectLibFlags = rights $ map unwrapStringXObj flags}
 projectSetLibFlags _ _ = Left "can't use non-string as library flag"
 
 -- | Get the pkg-config flags for the project.
@@ -96,21 +86,11 @@ projectGetPkgConfigFlags proj =
    in wrapArray (map wrapString fs)
 
 -- | Set the project's pkg-config flags
---
--- NOTE: This retains existing behavior in which one can only add one flag at
--- a time and the flags are append only. A slightly more functional interface
--- would take a list of flags as arguments; e.g. to add *one* flag:
---
---   (Project.config "pkgconfigflags" (cons "-lmylib" (Project.get-config
---   "pkgconfigflags")))
---
---   or to wipe the flags whole-cloth (e.g. for a different target)
---
---   (Project.config "pkgconfigflags" ("-lmy" "-lnew" "-llibflags"))
---
---   likewise for flag removal etc.
 projectSetPkgConfigFlags :: ProjectSetter
-projectSetPkgConfigFlags proj (XObj (Str flag) _ _) = Right (proj {projectPkgConfigFlags = addIfNotPresent flag (projectPkgConfigFlags proj)})
+projectSetPkgConfigFlags proj (XObj (Lst flags) _ _) =
+  if not $ all isStr flags
+    then Left "can't use a non-string as a C compiler library flag"
+    else Right proj {projectPkgConfigFlags = rights $ map unwrapStringXObj flags}
 projectSetPkgConfigFlags _ _ = Left "can't use non-string as pkg-config flag"
 
 projectGetEchoC :: ProjectGetter