metal : return null instead of exit(1) (#2573)

Author: jhen0409

ggml-metal.m

@@ -126,7 +126,7 @@ @implementation GGMLMetalClass
         ctx->library = [ctx->device newLibraryWithSource:msl_library_source options:nil error:&error];
         if (error) {
             fprintf(stderr, "%s: error: %s\n", __func__, [[error description] UTF8String]);
-            exit(1);
+            return NULL;
         }
     }
 #else
@@ -144,7 +144,7 @@ @implementation GGMLMetalClass
         NSString * src  = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];
         if (error) {
             fprintf(stderr, "%s: error: %s\n", __func__, [[error description] UTF8String]);
-            exit(1);
+            return NULL;
         }
 
 #ifdef GGML_QKK_64
@@ -156,7 +156,7 @@ @implementation GGMLMetalClass
 #endif
         if (error) {
             fprintf(stderr, "%s: error: %s\n", __func__, [[error description] UTF8String]);
-            exit(1);
+            return NULL;
         }
     }
 #endif

llama.cpp

@@ -3337,6 +3337,12 @@ struct llama_context * llama_new_context_with_model(
         // this allocates all Metal resources and memory buffers
         ctx->ctx_metal = ggml_metal_init(1);
 
+        if (!ctx->ctx_metal) {
+            LLAMA_LOG_ERROR("%s: ggml_metal_init() failed\n", __func__);
+            llama_free(ctx);
+            return NULL;
+        }
+
         void * data_ptr  = NULL;
         size_t data_size = 0;