target/register: use an array of uint8_t for register's value

The use of 'void *' makes the pointer arithmetic incompatible with
standard C, even if this is allowed by GCC extensions.
The use of 'void *' can also hide incorrect pointer assignments.

Switch to 'uint8_t *' and add GCC warning flag to track any use of
pointer arithmetic extension.

Change-Id: Ic4d15a232834cd6b374330f70e2473a359b1607f
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5937
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

configure.ac

@@ -833,6 +833,7 @@ AS_IF([test "x${gcc_wextra}" = "xyes"], [
   GCC_WARNINGS="${GCC_WARNINGS} -Wbad-function-cast"
   GCC_WARNINGS="${GCC_WARNINGS} -Wcast-align"
   GCC_WARNINGS="${GCC_WARNINGS} -Wredundant-decls"
+  GCC_WARNINGS="${GCC_WARNINGS} -Wpointer-arith"
 ])
 AS_IF([test "x${gcc_werror}" = "xyes"], [
   GCC_WARNINGS="${GCC_WARNINGS} -Werror"

src/target/arc.c

@@ -305,7 +305,7 @@ static int arc_init_reg(struct target *target, struct reg *reg,
 	/* Initialize struct reg */
 	reg->name = reg_desc->name;
 	reg->size = 32; /* All register in ARC are 32-bit */
-	reg->value = &reg_desc->reg_value;
+	reg->value = reg_desc->reg_value;
 	reg->type = &arc_reg_type;
 	reg->arch_info = reg_desc;
 	reg->caller_save = true; /* @todo should be configurable. */

src/target/arm7_9_common.c

@@ -1393,7 +1393,7 @@ static int arm7_9_full_context(struct target *target)
 	struct arm *arm = &arm7_9->arm;
 	struct {
 		uint32_t value;
-		void *reg_p;
+		uint8_t *reg_p;
 	} read_cache[6 * (16 + 1)];
 	int read_cache_idx = 0;
 

src/target/etm.c

@@ -279,7 +279,7 @@ static void etm_reg_add(unsigned bcd_vers, struct arm_jtag *jtag_info,
 
 		reg->name = r->name;
 		reg->size = r->size;
-		reg->value = &ereg->value;
+		reg->value = ereg->value;
 		reg->arch_info = ereg;
 		reg->type = &etm_scan6_type;
 		reg++;

src/target/register.h

@@ -127,7 +127,7 @@ struct reg {
 	bool caller_save;
 	/* Pointer to place where the value is stored, in the format understood by
 	 * the binarybuffer.h functions. */
-	void *value;
+	uint8_t *value;
 	/* The stored value needs to be written to the target. */
 	bool dirty;
 	/* When true, value is valid. */

src/target/riscv/riscv.c

@@ -4128,7 +4128,7 @@ int riscv_init_registers(struct target *target)
 		reg_name += strlen(reg_name) + 1;
 		assert(reg_name < info->reg_names + target->reg_cache->num_regs *
 				max_reg_name_len);
-		r->value = &info->reg_cache_values[number];
+		r->value = info->reg_cache_values[number];
 	}
 
 	return ERROR_OK;

src/target/riscv/riscv.h

@@ -68,8 +68,8 @@ typedef struct {
 
 	/* OpenOCD's register cache points into here. This is not per-hart because
 	 * we just invalidate the entire cache when we change which hart is
-	 * selected. */
-	uint64_t reg_cache_values[RISCV_MAX_REGISTERS];
+	 * selected. Use an array of 8 uint8_t per register. */
+	uint8_t reg_cache_values[RISCV_MAX_REGISTERS][8];
 
 	/* Single buffer that contains all register names, instead of calling
 	 * malloc for each register. Needs to be freed when reg_list is freed. */