[Warnings] Simplified String Allocation

GCC sometimes gets confused with how strings are allocated, when they
are C strings allocated by hand. Tried to simplify the allocation to
make it more obvious. In the future this should be replaced with a
vector.

Author: AlexandreSinger

vpr/src/power/power_util.cpp

@@ -217,10 +217,11 @@ char* alloc_SRAM_values_from_truth_table(int LUT_size,
 
     //SRAM value stored as a string of '0' and '1' characters
     // Initialize to all zeros
-    char* SRAM_values = new char[num_SRAM_bits + 1];
+    size_t SRAM_values_str_size = num_SRAM_bits + 1;
+    char* SRAM_values = new char[SRAM_values_str_size];
     for (size_t i = 0; i < num_SRAM_bits + 1; i++)
         SRAM_values[i] = '0';
-    SRAM_values[num_SRAM_bits] = '\0';
+    SRAM_values[SRAM_values_str_size - 1] = '\0';
 
     if (truth_table.empty()) {
         for (size_t i = 0; i < num_SRAM_bits; i++) {