Switch to snprintf in chat() for out of bounds safety

Also end prompt that's passed via command line with \n, as this is
necessary for some frames and we get \n from fgets() normally.

src/run.c

@@ -334,19 +334,15 @@ static const char* chatframe(const char* style, bool has_system) {
 }
 
 void chat(struct Transformer* transformer, struct Tokenizer* tokenizer, struct Sampler* sampler, char* cli_prompt, char* system_prompt, const char* arch) {
-
-	// buffers for reading the system prompt and user prompt from stdin
-	// you'll notice they are soomewhat haphazardly and unsafely set atm
 	char user_prompt[512];
-	char rendered_prompt[1152];
+	char rendered_prompt[sizeof(user_prompt) * 2];
+	int prompt_tokens[sizeof(rendered_prompt) + 4];
 	int num_prompt_tokens = 0;
-	int* prompt_tokens = (int*)malloc(1152 * sizeof(int));
-	int user_idx;
 
-	// start the main loop
+	int user_idx = 0;
 	int user_turn = 1; // user starts
 	int next = 0;      // will store the next token in the sequence
-	int token;         // stores the current token to feed into the transformer
+	int token = 0;     // stores the current token to feed into the transformer
 	int pos = 0;       // position in the sequence
 	for (;;) {
 
@@ -355,7 +351,7 @@ void chat(struct Transformer* transformer, struct Tokenizer* tokenizer, struct S
 			// get the user prompt
 			if (pos == 0 && cli_prompt != NULL) {
 				// user prompt for position 0 was passed in, use it
-				strcpy(user_prompt, cli_prompt);
+				snprintf(user_prompt, sizeof(user_prompt), "%s\n", cli_prompt);
 			} else {
 				// otherwise get user prompt from stdin
 				double seq_pct = (double)pos / (double)transformer->config.seq_len;
@@ -371,9 +367,9 @@ void chat(struct Transformer* transformer, struct Tokenizer* tokenizer, struct S
 			// render user/system prompts into the chat schema
 			const char* style = tokenizer->eot_id >= 0 ? "llama3" : arch;
 			if (pos == 0 && system_prompt[0] != '\0') {
-				sprintf(rendered_prompt, chatframe(style, true), system_prompt, user_prompt);
+				snprintf(rendered_prompt, sizeof(rendered_prompt), chatframe(style, true), system_prompt, user_prompt);
 			} else {
-				sprintf(rendered_prompt, chatframe(style, false), user_prompt);
+				snprintf(rendered_prompt, sizeof(rendered_prompt), chatframe(style, false), user_prompt);
 			}
 
 			// encode the rendered prompt into tokens
@@ -412,8 +408,6 @@ void chat(struct Transformer* transformer, struct Tokenizer* tokenizer, struct S
 			}
 		}
 	}
-
-	free(prompt_tokens);
 }
 
 // ----------------------------------------------------------------------------