shared.c: use execvp() to execute filter commands

This reintroduces the use of execvp(), since the filter commands doesn't
always contain an absolute path (i.e. snapshot compression filters).

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

shared.c

@@ -383,7 +383,7 @@ typedef struct {
 	char * value;
 } cgit_env_var;
 
-static char * prepare_env(struct cgit_repo * repo) {
+static void prepare_env(struct cgit_repo * repo) {
 	cgit_env_var env_vars[] = {
 		{ .name = "CGIT_REPO_URL", .value = repo->url },
 		{ .name = "CGIT_REPO_NAME", .value = repo->name },
@@ -394,52 +394,14 @@ static char * prepare_env(struct cgit_repo * repo) {
 		{ .name = "CGIT_REPO_CLONE_URL", .value = repo->clone_url }
 	};
 	int env_var_count = ARRAY_SIZE(env_vars);
-	long values_space = (env_var_count * (PATH_MAX + 64));
-
-	void * buffer;
-	char ** vars;
-	char * values;
-	int vars_index = 0;
-	unsigned int chars_printed;
-
-	/* Allocate buffer for environment variables: first in the buffer is an
-	 * array of pointers to argument strings, terminated with a NULL pointer.
-	 * After that the argument strings are placed after each other */
-	buffer = malloc(((env_var_count + 1) * sizeof(char *)) + values_space);
-	if (!buffer)
-		return NULL;
-
-	vars = buffer;
-	values = (char *) &vars[env_var_count + 1];
-
-	/* loop over all defined environment variables and their values */
-	while (vars_index < env_var_count) {
-		char * name = env_vars[vars_index].name;
-		char * value = env_vars[vars_index].value;
-
-		if (!value)
-			value = "";
-
-		chars_printed = snprintf(values, (values_space - 1), "%s=%s", name,
-				value);
-		if (chars_printed > (values_space - 1)) {
-			/* Buffer space exhausted: stop adding variables.
-			 * Not all environment variables are defined, but the best we can
-			 * do is to provide the ones that _are_ defined */
-			break;
-		}
-
-		values[chars_printed] = '\0';
-		*&vars[vars_index] = values;
-		values += (chars_printed + 1);
-		values_space -= (chars_printed + 1);
-		vars_index++;
-	}
-
-	/* terminate the array with pointers */
-	*&vars[vars_index] = NULL;
-
-	return (char *) buffer;
+	cgit_env_var *p, *q;
+	static char *warn = "cgit warning: failed to set env: %s=%s\n";
+
+	p = env_vars;
+	q = p + env_var_count;
+	for (; p < q; p++)
+		if (setenv(p->name, p->value, 1))
+			fprintf(stderr, warn, p->name, p->value);
 }
 
 int cgit_open_filter(struct cgit_filter *filter, struct cgit_repo * repo)
@@ -450,20 +412,12 @@ int cgit_open_filter(struct cgit_filter *filter, struct cgit_repo * repo)
 	chk_zero(pipe(filter->pipe_fh), "Unable to create pipe to subprocess");
 	filter->pid = chk_non_negative(fork(), "Unable to create subprocess");
 	if (filter->pid == 0) {
-		char * env = NULL;
-
 		close(filter->pipe_fh[1]);
 		chk_non_negative(dup2(filter->pipe_fh[0], STDIN_FILENO),
 			"Unable to use pipe as STDIN");
-
 		if (repo)
-			env = prepare_env(repo);
-
-		execve(filter->cmd, filter->argv, (char **)env);
-
-		if (env)
-			free(env);
-
+			prepare_env(repo);
+		execvp(filter->cmd, filter->argv);
 		die("Unable to exec subprocess %s: %s (%d)", filter->cmd,
 			strerror(errno), errno);
 	}