mtmd: explicitly forbidden inclusion of private header and libcommon (#17946)

tools/mtmd/CMakeLists.txt

@@ -53,6 +53,15 @@ if (TARGET BUILD_INFO)
     add_dependencies(mtmd-helper BUILD_INFO)
 endif()
 
+# if mtmd is linked against common, we throw an error
+if (TARGET mtmd)
+    get_target_property(libs mtmd LINK_LIBRARIES)
+    if (libs AND "common" IN_LIST libs)
+        message(FATAL_ERROR "mtmd is designed to be a public library.\n"
+                            "It must not link against common")
+    endif()
+endif()
+
 add_executable(llama-llava-cli    deprecation-warning.cpp)
 add_executable(llama-gemma3-cli   deprecation-warning.cpp)
 add_executable(llama-minicpmv-cli deprecation-warning.cpp)

tools/mtmd/clip-impl.h

@@ -13,6 +13,8 @@
 
 // Internal header for clip.cpp
 
+#define MTMD_INTERNAL_HEADER
+
 #define KEY_FTYPE               "general.file_type"
 #define KEY_NAME                "general.name"
 #define KEY_DESCRIPTION         "general.description"

tools/mtmd/clip.h

@@ -7,6 +7,8 @@
 
 // !!! Internal header, to be used by mtmd only !!!
 
+#define MTMD_INTERNAL_HEADER
+
 struct clip_ctx;
 
 struct clip_image_size {

tools/mtmd/mtmd-audio.h

@@ -6,6 +6,8 @@
 #include <vector>
 #include <string>
 
+#define MTMD_INTERNAL_HEADER
+
 #define WHISPER_ASSERT GGML_ASSERT
 
 #define WHISPER_SAMPLE_RATE 16000

tools/mtmd/mtmd-helper.cpp

@@ -32,6 +32,10 @@
 #define STB_IMAGE_IMPLEMENTATION
 #include "stb/stb_image.h"
 
+#ifdef MTMD_INTERNAL_HEADER
+#error "mtmd-helper is a public library outside of mtmd. it must not include internal headers"
+#endif
+
 //
 // internal logging functions
 //