Re: [PATCH v2 03/19] powerpc: Mark variables as unused

[LEROY Christophe]

Michael Ellerman <m...@ellerman.id.au> a écrit :

LEROY Christophe <christophe.le...@c-s.fr> writes:

Mathieu Malaterre <ma...@debian.org> a écrit :

Add gcc attribute unused for two variables. Fix warnings treated as errors
with W=1:

  arch/powerpc/kernel/prom_init.c:1388:8: error: variable ‘path’ set
but not used [-Werror=unused-but-set-variable]

Suggested-by: Christophe Leroy <christophe.le...@c-s.fr>
Signed-off-by: Mathieu Malaterre <ma...@debian.org>
---
v2: move path within ifdef DEBUG_PROM

 arch/powerpc/kernel/prom_init.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/prom_init.c
b/arch/powerpc/kernel/prom_init.c
index acf4b2e0530c..4163b11abb6c 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -603,7 +603,7 @@ static void __init early_cmdline_parse(void)
        const char *opt;

        char *p;
-       int l = 0;
+       int l __maybe_unused = 0;

        prom_cmd_line[0] = 0;
        p = prom_cmd_line;
@@ -1385,7 +1385,7 @@ static void __init reserve_mem(u64 base, u64 size)
 static void __init prom_init_mem(void)
 {
        phandle node;
-       char *path, type[64];
+       char *path __maybe_unused, type[64];

You should enclose that in an ifdef DEBUG_PROM instead of hiding the warning

I disagree, the result is horrible:

 static void __init prom_init_mem(void)
 {
        phandle node;
-       char *path, type[64];
+#ifdef DEBUG_PROM
+       char *path;
+#endif
+       char type[64];
        unsigned int plen;
        cell_t *p, *endp;
        __be32 val;


The right fix is to move the debug logic into a helper, and put the path
in there, eg. something like (not tested):

diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c

index f9d6befb55a6..b02fa2ccc70b 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -1389,6 +1389,18 @@ static void __init reserve_mem(u64 base, u64 size)
        mem_reserve_cnt = cnt + 1;
 }

+#ifdef DEBUG_PROM
+static void prom_debug_path(phandle node)
+{
+       char *path;
+       path = prom_scratch;
+       memset(path, 0, PROM_SCRATCH_SIZE);
+       call_prom("package-to-path", 3, 1, node, path, PROM_SCRATCH_SIZE-1);
+       prom_debug("  node %s :\n", path);
+}
+#else
+static void prom_debug_path(phandle node) { }

Or put the ifdef inside the function to avoid double definition ?

+#endif /* DEBUG_PROM */
 /*
  * Initialize memory allocation mechanism, parse "memory" nodes and
  * obtain that way the top of memory and RMO to setup out local allocator
@@ -1441,11 +1453,7 @@ static void __init prom_init_mem(void)
                p = regbuf;
                endp = p + (plen / sizeof(cell_t));

-#ifdef DEBUG_PROM
-               memset(path, 0, PROM_SCRATCH_SIZE);
-               call_prom("package-to-path", 3, 1, node, path, 
PROM_SCRATCH_SIZE-1);
-               prom_debug("  node %s :\n", path);
-#endif /* DEBUG_PROM */
+               prom_debug_path(node);

                while ((endp - p) >= (rac + rsc)) {
                        unsigned long base, size;


Although that also begs the question of why the hell do we need path at
all, and not just use prom_scratch directly?

Wondering the same, why not use prom_scratch directly

Christophe

cheers