selftests/bpf: Fix conflicts with built-in functions in bpf_iter_ksym

Both tolower and toupper are built in c functions, we should not
redefine them as this can result in a build error.

Fixes the following errors:
progs/bpf_iter_ksym.c:10:20: error: conflicting types for built-in function 'tolower'; expected 'int(int)' [-Werror=builtin-declaration-mismatch]
   10 | static inline char tolower(char c)
      |                    ^~~~~~~
progs/bpf_iter_ksym.c:5:1: note: 'tolower' is declared in header '<ctype.h>'
    4 | #include <bpf/bpf_helpers.h>
  +++ |+#include <ctype.h>
    5 |
progs/bpf_iter_ksym.c:17:20: error: conflicting types for built-in function 'toupper'; expected 'int(int)' [-Werror=builtin-declaration-mismatch]
   17 | static inline char toupper(char c)
      |                    ^~~~~~~
progs/bpf_iter_ksym.c:17:20: note: 'toupper' is declared in header '<ctype.h>'

See background on this sort of issue:
https://stackoverflow.com/a/20582607
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=12213

(C99, 7.1.3p1) "All identifiers with external linkage in any of the
following subclauses (including the future library directions) are
always reserved for use as identifiers with external linkage."

This is documented behavior in GCC:
https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-std-2

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20221203010847.2191265-1-james.hilliard1@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c b/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c
index 285c008cbf9c2785c5b7022f70fd214e866c5386..9ba14c37bbcc925da01da0c493b75860de31fef1 100644 (file)
--- a/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c
@@ -7,14 +7,14 @@ char _license[] SEC("license") = "GPL";
 
 unsigned long last_sym_value = 0;
 
-static inline char tolower(char c)
+static inline char to_lower(char c)
 {
        if (c >= 'A' && c <= 'Z')
                c += ('a' - 'A');
        return c;
 }
 
-static inline char toupper(char c)
+static inline char to_upper(char c)
 {
        if (c >= 'a' && c <= 'z')
                c -= ('a' - 'A');
@@ -54,7 +54,7 @@ int dump_ksym(struct bpf_iter__ksym *ctx)
        type = iter->type;
 
        if (iter->module_name[0]) {
-               type = iter->exported ? toupper(type) : tolower(type);
+               type = iter->exported ? to_upper(type) : to_lower(type);
                BPF_SEQ_PRINTF(seq, "0x%llx %c %s [ %s ] ",
                               value, type, iter->name, iter->module_name);
        } else {