实例详解——编译器命令#pragma section作用于函数时作用域是否覆盖到其子函数

在之前的博客【链接脚本（Linker Script）应用实例（一）使用copy table将函数载入到RAM中运行】中，我们第一步使用#pragma section命令将PFlashProgram函数存储至程序段.flash_driver，具体程序如下：

#pragma section ".flash_driver" ax

void PFlashProgram( uint32 flash, uint32 addr, uint32 word_l, uint32 word_u )
{
    uint32 load_cnt;
    uint16 endinitSfty_pw = IfxScuWdt_getSafetyWatchdogPasswordInline();

    IfxFlash_enterPageMode(addr);

    /* wait until unbusy */
    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);

    /* write 32 bytes (8 doublewords) into assembly buffer */
    ; load_cnt < ; load_cnt++)
    {
        IfxFlash_loadPage2X32(addr, word_l, word_u);
    }

    /* write page */
    IfxScuWdt_clearSafetyEndinitInline(endinitSfty_pw);
    IfxFlash_writePage(addr);
    IfxScuWdt_setSafetyEndinitInline(endinitSfty_pw);

    /* wait until unbusy */
    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);
}
#pragma section

编译之后的map文件如下，可以看到PFlashProgram函数生成的程序段大小为280字节。下面对函数的内容进行调整后重新编译，以验证将PFlashProgram函数存储到.flash_driver程序段时是否同时也将IfxFlash_enterPageMode、IfxFlash_waitUnbusy及IfxFlash_loadPage2X32等子函数同时存储到该段。这个问题之所以值得关注，是因为若不将其子函数也存储到该段，子函数将默认存储在ROM（Flash）中，那么PFlashProgram函数执行到其子函数时将从Flash而不是RAM中取指令。由于TC297不支持Flash操作函数对其所在的Flash进行擦写（Flash大多都具有这种特性）（Flash操作函数必须在RAM中或另一个Flash Bank中运行从而执行擦写操作），PFlashProgram函数无法成功执行对PFlash的写入操作。另外，了解#pragma section命令的这个特性也有助于程序员对代码存储与执行情况的掌握。

Linker version: GNU ld version (GNU Binutils) 2.20 (TriCore) using BFD version (GNU Binutils) 2.20 (v2.3), Tool Version v2.7
Name of linker executable: c:/hightec/toolchains/tricore/v4.9.1.0-infineon-2.0/bin/../lib/gcc/tricore/4.9.4/../../../../tricore/bin/ld.exe
Date of link run: Thu Sep 05 10:42:28 2019
Name of linker map file: Flash_test.map

>>> Symbols (global (S = g) and static (S = l); sorted by address)

============================================================================================================================================================
Start      End        Size S Name                                   Memory      O-Sec        I-Sec         Input object
============================================================================================================================================================
 g __TRICORE_DERIVATE_MEMORY_MAP__        *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK0_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK1_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK2_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_HEAP_SIZE                          *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_USTACK0_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_USTACK1_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_USTACK2_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*

......................

 g __TRAPTAB_CPU2                         pfls0       .traptab_tc2 .traptab_tc2  Flash_test.elf
 g IfxCpu_Trap_vectorTable1               pfls0       .traptab_tc1 .traptab_cpu1 0_Src\4_McHal\Tricore\Cpu\Trap\IfxCpu_Trap.o
 g LCF_TRAPVEC1_START                     *ABS*       *ABS*        *ABS*         *ABS*
 g __TRAPTAB_CPU1                         pfls0       .traptab_tc1 .traptab_tc1  Flash_test.elf
 g _SMALL_DATA4_                          *ABS*       *ABS*        *ABS*         *ABS*
 g __A9_MEM                               *ABS*       *ABS*        *ABS*         *ABS*
 g PFlashProgram                          psram_local .code2ram    .flash_driver 0_Src\0_AppSw\Tricore\Demo_Illd\FlashDemo.o

（1）首先注释掉与Flash操作相关的5个子函数，然后重新编译，查看map文件。可见PFlashProgram函数产生的程序段大小变为136字节，这是否说明这5个Flash操作函数对应的程序段大小为144（280-136）字节呢？我们继续进行测试

#pragma section ".flash_driver" ax

void PFlashProgram( uint32 flash, uint32 addr, uint32 word_l, uint32 word_u )
{
    uint32 load_cnt;
    uint16 endinitSfty_pw = IfxScuWdt_getSafetyWatchdogPasswordInline();

//    IfxFlash_enterPageMode(addr);

    /* wait until unbusy */
//    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);

    /* write 32 bytes (8 doublewords) into assembly buffer */
    ; load_cnt < ; load_cnt++)
    {
//        IfxFlash_loadPage2X32(addr, word_l, word_u);
    }

    /* write page */
    IfxScuWdt_clearSafetyEndinitInline(endinitSfty_pw);
//    IfxFlash_writePage(addr);
    IfxScuWdt_setSafetyEndinitInline(endinitSfty_pw);

    /* wait until unbusy */
//    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);
}
#pragma section

Linker version: GNU ld version (GNU Binutils) 2.20 (TriCore) using BFD version (GNU Binutils) 2.20 (v2.3), Tool Version v2.7
Name of linker executable: c:/hightec/toolchains/tricore/v4.9.1.0-infineon-2.0/bin/../lib/gcc/tricore/4.9.4/../../../../tricore/bin/ld.exe
Date of link run: Thu Sep 05 18:34:08 2019
Name of linker map file: Flash_test.map

>>> Symbols (global (S = g) and static (S = l); sorted by address)

============================================================================================================================================================
Start      End        Size S Name                                   Memory      O-Sec        I-Sec         Input object
============================================================================================================================================================
 g __TRICORE_DERIVATE_MEMORY_MAP__        *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK0_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK1_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK2_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
..........
 g __TRAPTAB_CPU1                         pfls0       .traptab_tc1 .traptab_tc1  Flash_test.elf
 g _SMALL_DATA4_                          *ABS*       *ABS*        *ABS*         *ABS*
 g __A9_MEM                               *ABS*       *ABS*        *ABS*         *ABS*
 g PFlashProgram                          psram_local .code2ram    .flash_driver 0_Src\0_AppSw\Tricore\Demo_Illd\FlashDemo.o

现在，我们注释掉5个Flash操作函数以外的代码，map文件如下。可以看到PFlashProgram的大小变为146字节而不是之前推测的144字节。为什么多出2字节呢？我们接下来将整个函数体内部的语句全部注释掉试试，看看函数的“框架”占用多大空间。

#pragma section ".flash_driver" ax

void PFlashProgram( uint32 flash, uint32 addr, uint32 word_l, uint32 word_u )
{
//    uint32 load_cnt;
//    uint16 endinitSfty_pw = IfxScuWdt_getSafetyWatchdogPasswordInline();

    IfxFlash_enterPageMode(addr);

    /* wait until unbusy */
    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);

    /* write 32 bytes (8 doublewords) into assembly buffer */
//    for (load_cnt = 0; load_cnt < 4; load_cnt++)
//    {
        IfxFlash_loadPage2X32(addr, word_l, word_u);
//    }

    /* write page */
//    IfxScuWdt_clearSafetyEndinitInline(endinitSfty_pw);
    IfxFlash_writePage(addr);
//    IfxScuWdt_setSafetyEndinitInline(endinitSfty_pw);

    /* wait until unbusy */
    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);
}
#pragma section

Linker version: GNU ld version (GNU Binutils) 2.20 (TriCore) using BFD version (GNU Binutils) 2.20 (v2.3), Tool Version v2.7
Name of linker executable: c:/hightec/toolchains/tricore/v4.9.1.0-infineon-2.0/bin/../lib/gcc/tricore/4.9.4/../../../../tricore/bin/ld.exe
Date of link run: Thu Sep 05 18:45:58 2019
Name of linker map file: Flash_test.map

>>> Symbols (global (S = g) and static (S = l); sorted by address)

============================================================================================================================================================
Start      End        Size S Name                                   Memory      O-Sec        I-Sec         Input object
============================================================================================================================================================
 g __TRICORE_DERIVATE_MEMORY_MAP__        *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK0_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK1_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK2_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
..........
 g __TRAPTAB_CPU1                         pfls0       .traptab_tc1 .traptab_tc1  Flash_test.elf
 g _SMALL_DATA4_                          *ABS*       *ABS*        *ABS*         *ABS*
 g __A9_MEM                               *ABS*       *ABS*        *ABS*         *ABS*
 g PFlashProgram                          psram_local .code2ram    .flash_driver 0_Src\0_AppSw\Tricore\Demo_Illd\FlashDemo.o

由map文件可以看到，这个空的函数大小为2字节。到这里我们知道函数总大小为280字节，其中函数“框架”占2字节，5个Flash操作函数占144字节，其他语句和函数占134字节。

到此，我们可以得出本篇博文最重要的结论：#pragma section命令将一个函数存储到程序段时，会将其调用的子函数也一起存储到该段中。

#pragma section ".flash_driver" ax

void PFlashProgram( uint32 flash, uint32 addr, uint32 word_l, uint32 word_u )
{
//    uint32 load_cnt;
//    uint16 endinitSfty_pw = IfxScuWdt_getSafetyWatchdogPasswordInline();

//    IfxFlash_enterPageMode(addr);

    /* wait until unbusy */
//    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);

    /* write 32 bytes (8 doublewords) into assembly buffer */
//    for (load_cnt = 0; load_cnt < 4; load_cnt++)
//    {
//        IfxFlash_loadPage2X32(addr, word_l, word_u);
//    }

    /* write page */
//    IfxScuWdt_clearSafetyEndinitInline(endinitSfty_pw);
//    IfxFlash_writePage(addr);
//    IfxScuWdt_setSafetyEndinitInline(endinitSfty_pw);

    /* wait until unbusy */
//    IfxFlash_waitUnbusy(flash, IfxFlash_FlashType_P0);
}
#pragma section

Linker version: GNU ld version (GNU Binutils) 2.20 (TriCore) using BFD version (GNU Binutils) 2.20 (v2.3), Tool Version v2.7
Name of linker executable: c:/hightec/toolchains/tricore/v4.9.1.0-infineon-2.0/bin/../lib/gcc/tricore/4.9.4/../../../../tricore/bin/ld.exe
Date of link run: Thu Sep 05 18:52:56 2019
Name of linker map file: Flash_test.map

>>> Symbols (global (S = g) and static (S = l); sorted by address)

============================================================================================================================================================
Start      End        Size S Name                                   Memory      O-Sec        I-Sec         Input object
============================================================================================================================================================
 g __TRICORE_DERIVATE_MEMORY_MAP__        *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK0_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK1_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
 g LCF_ISTACK2_SIZE                       *ABS*       *ABS*        *ABS*         *ABS*
..........
 g __TRAPTAB_CPU1                         pfls0       .traptab_tc1 .traptab_tc1  Flash_test.elf
 g _SMALL_DATA4_                          *ABS*       *ABS*        *ABS*         *ABS*
 g __A9_MEM                               *ABS*       *ABS*        *ABS*         *ABS*
 g PFlashProgram                          psram_local .code2ram    .flash_driver 0_Src\0_AppSw\Tricore\Demo_Illd\FlashDemo.o