bpftool: Fix maybe-uninitialized warnings

Somehow when bpftool is compiled in -Og mode, compiler produces new warnings
about possibly uninitialized variables. Fix all the reported problems.

Fixes: 2119f2189d ("bpftool: add C output format option to btf dump subcommand")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210313210920.1959628-3-andrii@kernel.org

tools/bpf/bpftool/btf.c

@@ -546,6 +546,7 @@ static int do_dump(int argc, char **argv)
 			NEXT_ARG();
 			if (argc < 1) {
 				p_err("expecting value for 'format' option\n");
+				err = -EINVAL;
 				goto done;
 			}
 			if (strcmp(*argv, "c") == 0) {
@@ -555,11 +556,13 @@ static int do_dump(int argc, char **argv)
 			} else {
 				p_err("unrecognized format specifier: '%s', possible values: raw, c",
 				      *argv);
+				err = -EINVAL;
 				goto done;
 			}
 			NEXT_ARG();
 		} else {
 			p_err("unrecognized option: '%s'", *argv);
+			err = -EINVAL;
 			goto done;
 		}
 	}

tools/bpf/bpftool/main.c

@@ -276,7 +276,7 @@ static int do_batch(int argc, char **argv)
 	int n_argc;
 	FILE *fp;
 	char *cp;
-	int err;
+	int err = 0;
 	int i;
 
 	if (argc < 2) {
@@ -370,7 +370,6 @@ static int do_batch(int argc, char **argv)
 	} else {
 		if (!json_output)
 			printf("processed %d commands\n", lines);
-		err = 0;
 	}
 err_close:
 	if (fp != stdin)

tools/bpf/bpftool/map.c

@@ -100,7 +100,7 @@ static int do_dump_btf(const struct btf_dumper *d,
 		       void *value)
 {
 	__u32 value_id;
-	int ret;
+	int ret = 0;
 
 	/* start of key-value pair */
 	jsonw_start_object(d->jw);