[PATCH][ARM][gas] Fix warnings about uninitialised uses and unused const variables

[Kyrill Tkachov]

Hi all,

I recently upgraded my host compiler to GCC 6.1.0 and while trying to build a
cross toolchain for arm-none-eabi I've encountered some -Werror errors in 
tc-arm.c
This patch fixes them.

Some static const variables that are unused are marked with ATTRIBUTE_UNUSED.
In parse_neon_el_struct_list GCC complains that firsttype.index may be used
uninitialized in an inlined neon_alias_types_same call.
This patch initialises the fields firsttype to prevent that.

With this patch the gas build succeeds for me.
Tested with make check-gas for arm-none-eabi.

Ok to commit?

Thanks,
Kyrill

2016-04-29  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    * config/tc-arm.c (fpu_arch_vfp_v1): Mark with ATTRIBUTE_UNUSED.
    (fpu_arch_vfp_v3): Likewise.
    (fpu_arch_neon_v1): Likewise.
    (arm_arch_full): Likewise.
    (parse_neon_el_struct_list): Initialize fields of firsttype.

diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index 958434b3563cb49c3fb3cd04ffefc396916f2a49..64d87a371058f0a5b1d173fa4cb43ba8f86dee0d 100644
--- a/gas/config/tc-arm.c
+++ b/gas/config/tc-arm.c
@@ -155,10 +155,10 @@ static const arm_feature_set *object_arch = NULL;
 
 /* Constants for known architecture features.  */
 static const arm_feature_set fpu_default = FPU_DEFAULT;
-static const arm_feature_set fpu_arch_vfp_v1 = FPU_ARCH_VFP_V1;
+static const arm_feature_set fpu_arch_vfp_v1 ATTRIBUTE_UNUSED = FPU_ARCH_VFP_V1;
 static const arm_feature_set fpu_arch_vfp_v2 = FPU_ARCH_VFP_V2;
-static const arm_feature_set fpu_arch_vfp_v3 = FPU_ARCH_VFP_V3;
-static const arm_feature_set fpu_arch_neon_v1 = FPU_ARCH_NEON_V1;
+static const arm_feature_set fpu_arch_vfp_v3 ATTRIBUTE_UNUSED = FPU_ARCH_VFP_V3;
+static const arm_feature_set fpu_arch_neon_v1 ATTRIBUTE_UNUSED = FPU_ARCH_NEON_V1;
 static const arm_feature_set fpu_arch_fpa = FPU_ARCH_FPA;
 static const arm_feature_set fpu_any_hard = FPU_ANY_HARD;
 static const arm_feature_set fpu_arch_maverick = FPU_ARCH_MAVERICK;
@@ -221,7 +221,7 @@ static const arm_feature_set arm_ext_fp16 =
   ARM_FEATURE_CORE_HIGH (ARM_EXT2_FP16_INST);
 
 static const arm_feature_set arm_arch_any = ARM_ANY;
-static const arm_feature_set arm_arch_full = ARM_FEATURE (-1, -1, -1);
+static const arm_feature_set arm_arch_full ATTRIBUTE_UNUSED = ARM_FEATURE (-1, -1, -1);
 static const arm_feature_set arm_arch_t2 = ARM_ARCH_THUMB2;
 static const arm_feature_set arm_arch_none = ARM_ARCH_NONE;
 static const arm_feature_set arm_arch_v6m_only = ARM_ARCH_V6M_ONLY;
@@ -1988,6 +1988,10 @@ parse_neon_el_struct_list (char **str, unsigned *pbase,
   const char *const incr_error = _("register stride must be 1 or 2");
   const char *const type_error = _("mismatched element/structure types in list");
   struct neon_typed_alias firsttype;
+  firsttype.defined = 0;
+  firsttype.eltype.type = NT_invtype;
+  firsttype.eltype.size = -1;
+  firsttype.index = -1;
 
   if (skip_past_char (&ptr, '{') == SUCCESS)
     leading_brace = 1;