[RFC PATCH v2 14/26] perf bpf: Add -Wextra to cflags for more warnings and fix them

[He Kuang]

Since -Wextra is used in perf tools, this patch adopts this cflags
into lib/bpf. It also fixes 'comparison between signed and unsigned
integer' errors reported afterward.

Signed-off-by: He Kuang <heku...@huawei.com>
---
 tools/lib/bpf/Makefile | 2 +-
 tools/lib/bpf/libbpf.c | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 1fb098d..65a64d8 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -126,7 +126,7 @@ endif
 
 # Append required CFLAGS
 override CFLAGS += $(EXTRA_WARNINGS)
-override CFLAGS += -Werror -Wall
+override CFLAGS += -Werror -Wall -Wextra
 override CFLAGS += -fPIC
 override CFLAGS += $(INCLUDES)
 
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a53cb579..ddbba35 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -443,7 +443,7 @@ bpf_object__init_maps(struct bpf_object *obj, void *data,
                      size_t size)
 {
        size_t nr_maps;
-       int i;
+       unsigned int i;
 
        nr_maps = size / sizeof(struct bpf_map_def);
        if (!data || !nr_maps) {
@@ -480,7 +480,7 @@ bpf_object__init_maps(struct bpf_object *obj, void *data,
 static int
 bpf_object__init_maps_name(struct bpf_object *obj)
 {
-       int i;
+       unsigned int i;
        Elf_Data *symbols = obj->efile.symbols;
 
        if (!symbols || obj->efile.maps_shndx < 0)
@@ -521,7 +521,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
        Elf *elf = obj->efile.elf;
        GElf_Ehdr *ep = &obj->efile.ehdr;
        Elf_Scn *scn = NULL;
-       int idx = 0, err = 0;
+       unsigned int idx = 0;
+       int err = 0;
 
        /* Elf is corrupted/truncated, avoid calling elf_strptr. */
        if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL)) {
-- 
1.8.5.2