Keil编程环境下STM32内存管理研究
非常简单的一个工程，没有用到任何IO操作，与STM32有关的仅仅只有芯片的选择，即其SRAM大小有区别。图1是工程示意图，从图中可以看出，除了自己编写的代码外，仅仅增加了2个文件，即system_stm32f10x.c和startup_stm32f10x_hd.s，其中为了对startup_stm32f10x_hd.s进行修改，将其从库文件夹复制到了项目文件夹中。
图1
代码1
int main()
{
int a,b,c,d;
a=10;b=20;
c=a+b;
for(;;);
}
myex1.c(3): warning: #550-D: variable "c" was set but never used
linking...
Program Size: Code=796 RO-data=336 RW-data=20 ZI-data=1636
FromELF: creating hex file...
"myex1.axf" - 0 Error(s), 1 Warning(s).
代码2
int main()
{ const int x=16;
int a,b,c,d;
a=10;b=20;
c=a+b;
for(;;);
}
myex1.c(2): warning: #177-D: variable "x" was declared but never referenced
myex1.c(3): warning: #550-D: variable "c" was set but never used
linking...
Program Size: Code=800 RO-data=336 RW-data=20 ZI-data=1636
FromELF: creating hex file...
"myex1.axf" - 0 Error(s), 2 Warning(s).
说明：
（1）Code增加了4字节
（2）其余没有任何变化
代码3
int main()
{ const int x=16;
int myArry[100];
int i;
int a,b,c,d;
a=10;b=20;
c=a+b;
for(i=0;i<100;i++)
myArry[i]=i;
for(;;);
}
myex1.c(2): warning: #177-D: variable "x" was declared but never referenced
myex1.c(3): warning: #550-D: variable "myArry" was set but never used
myex1.c(5): warning: #550-D: variable "c" was set but never used
myex1.c(5): warning: #177-D: variable "d" was declared but never referenced
linking...
Program Size: Code=816 RO-data=336 RW-data=20 ZI-data=1636
FromELF: creating hex file...
"myex1.axf" - 0 Error(s), 4 Warning(s).
分析：程序中增加了数组myArry，Code增加为816字节，但是RO-data等仍未变化
代码4
int main()
{ const int x=16;
int myArry[100]={1,2,3,4,5,6};
int i;
int a,b,c,d;
a=10;b=20;
c=a+b;
for(i=0;i<100;i++)
myArry[i]=i;
for(;;);
}
myex1.c(2): warning: #177-D: variable "x" was declared but never referenced
myex1.c(3): warning: #550-D: variable "myArry" was set but never used
myex1.c(5): warning: #550-D: variable "c" was set but never used
