Keil中使用arm section进行绝对地址定位并进行O2等级代码优化时报错： Error: L6982E

1. 当使用O0优化时，可以正常进行编译

2、当选择O2优化时，编译会报错

 3、在motor_id.c文件中，使用arm section来将数据指定到特定位置

#pragma arm section rwdata = ".ARM.__at_0x1100CE00"

Parameter1             _Parameter1 =

{

  ……

};

Parameter2             _Parameter2=

{

  ……

};

Parameter3             _Parameter3 =

{

  ……

};

Parameter4            _Parameter4=

{

  ……

};

#pragma arm section

程序原意是将_Parameter1、_Parameter2、_Parameter3、_Parameter4四个结构体中的数据都指定到0x1100CE00起始的位置，在O0优化等级下程序这样写没有问题，但在O2优化等级下程序会报错。

错误详细信息如下：

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce04 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce13.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce04 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce0c.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce04 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce30.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce04 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce04 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce13 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce0c.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce13 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce30.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce13 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce13 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce0c overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce30.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce0c overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce0c overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce30 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce30 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

.\Objects\Test 9843_2QX.axf: Error: L6982E: AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28 overlaps address range with AT section motor_id.o(.ARM.__at_0x1100CE00) with base 0x1100ce00 limit 0x1100ce28.

分析编译时的输出log，可以大概看出是几个结构体的位置分配发生错乱，如果想在O0优化等级下使用arm section将几个结构体指定到特定存储地址，需要将程序进行修改。

4、修改步骤3中的程序

#pragma arm section rwdata = ".ARM.__at_0x1100CE00"

Parameter1             _Parameter1 =

{

  ……

};

#pragma arm section

#pragma arm section rwdata = ".ARM.__at_0x1100CE04"  //04是_Parameter1结构体的大小

Parameter2             _Parameter2=

{

  ……

};

#pragma arm section

#pragma arm section rwdata = ".ARM.__at_0x1100CE08"  //08是_Parameter1 + _Parameter2结构体的大小

Parameter3             _Parameter3 =

{

  ……

};

#pragma arm section

#pragma arm section rwdata = ".ARM.__at_0x1100CE0C"  //0C是_Parameter1 + _Parameter2+ _Parameter3结构体的大小

Parameter4            _Parameter4=

{

  ……

};

#pragma arm section

此时再进行编译就会正常，而且程序大小也会变小。

5、Keil中几个代码优化等级的说明

Keil中代码优化等级主要有四个O0、O1、O2、O3，默认的优化等级为O2

O0：使用最低优化，多数优化都被关闭，生成的代码具有最多的调试信息。

O1：使用有限优化，未使用的内联函数、未使用的静态函数以及冗余代码

          都会被移除，指令会被重新排序以避免互锁的情况。生成的代码会被

          适度优化，并且比较适合调试。

O2：使用高度优化，根据处理器的特定行为优化程序代码，生成的代码为

         高度优化的，并且具有有限的调试信息。

O3：使用极端优化，根据时间/空间选项进行优化，默认为多文件编译，它

          可以提供最高等级的优化，但编译时间会稍微长些，软件调试信息也

          比较少。

一般情况下采用default即O2等级的代码优化即可，如果采用O1、O2，则代码空间会变大，但会多很多调试信息，而使用O3的话有时候会对代码业务逻辑产生影响，所以一般采用O2等级进行优化代码。