calloc returns 指向自身的指针
calloc returns a pointer to itself
我在 Tiva C launchpad (ARM Cortex M4) 上分配内存时遇到问题，我想做的是在某个时候动态分配指向另一个结构内部结构的指针 calloc() returns 一个指针，其值与存储指针的地址相同。
我觉得这有点难以解释，所以我编写了这段代码来说明我想做的事情并且在 here 上运行得很好，但在我的应用程序中它的运行方式不同.
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <stddef.h>
typedef struct
{
uint32_t Pin;
uint32_t Port;
} fGpio_Pin;
typedef struct
{
uint32_t Mode;
uint32_t nPins;
fGpio_Pin** Pins;
} fSpi_Mod;
fSpi_Mod* Spi;
void printSizes (void)
{
printf("Size of uint8_t: %i bytes.\n", sizeof(uint8_t));
printf("Size of uint16_t: %i bytes.\n", sizeof(uint16_t));
printf("Size of uint32_t: %i bytes.\n", sizeof(uint32_t));
printf("Size of uint64_t: %i bytes.\n", sizeof(uint64_t));
printf("Size of fSpi_Mod*: %i bytes.\n", sizeof(fSpi_Mod*));
printf("Size of fSpi_Mod: %i bytes.\n", sizeof(fSpi_Mod));
printf("Size of fGpio_Pin**: %i bytes.\n", sizeof(fGpio_Pin**));
printf("Size of fGpio_Pin*: %i bytes.\n", sizeof(fGpio_Pin*));
printf("Size of fGpio_Pin: %i bytes.\n", sizeof(fGpio_Pin));
printf("----\n");
}
void printStructure (fSpi_Mod* Spi_Mod)
{
uint8_t i;
printf("The address of the structure is 0x%X.\n", Spi_Mod);
printf("The value of mode is 0x%X and address 0x%X.\n", Spi_Mod->Mode, &(Spi_Mod->Mode));
printf("The value of nPins is 0x%X and address 0x%X.\n", Spi_Mod->nPins, &(Spi_Mod->nPins));
printf("The value of Pins is 0x%X and address 0x%X.\n", Spi_Mod->Pins, &(Spi_Mod->Pins));
for (i = 0; i < Spi_Mod->nPins; i++)
{
printf("#%i | The pointer that points to Gpio structure is 0x%X at address 0x%X.\n", i, *(Spi_Mod->Pins + i), &(*(Spi_Mod->Pins + i)));
printf("#%i | The value of Pin of Gpio structure is 0x%X and address 0x%X.\n", i, ((*(Spi_Mod->Pins + i)))->Pin, &(((*(Spi_Mod->Pins + i)))->Pin));
printf("#%i | The value of Port of Gpio structure is 0x%X and address 0x%X.\n", i, ((*(Spi_Mod->Pins + i)))->Port, &(((*(Spi_Mod->Pins + i)))->Port));
}
printf("----\n");
}
int main()
{
uint8_t i = 0;
printf(">>>> Begin program.\n");
printSizes();
Spi = (fSpi_Mod*) calloc(1, sizeof(fSpi_Mod));
if (Spi == NULL) {
printf("Insufficient memory.\n");
return 1;
}
//printStructure(Spi);
Spi->Mode = 0x05;
Spi->nPins = 0x04;
Spi->Pins = (fGpio_Pin**) calloc(Spi->nPins, sizeof(fGpio_Pin*));
if (Spi->Pins == NULL)
{
printf("Insufficient memory.\n");
return 1;
}
//printStructure(Spi);
for (i = 0; i < Spi->nPins; i++)
{
(*(Spi->Pins + i)) = (fGpio_Pin*) calloc(1, sizeof(fGpio_Pin));
if ((*(Spi->Pins + i)) == NULL)
{
printf("Insufficient memory.\n");
return 1;
}
}
printStructure(Spi);
printf(">>>> End program.\n");
}
在我的应用程序中，当我尝试分配四个 "pointer to (fGpio_Pin*)" 类型的指针并将其转换为 (fGpio_Pin**) 时，calloc() returns [=17 的地址=]，所以基本上Spi->Pins的地址和它的值是一样的，就变成了指向它自己的指针，这时候问题就开始出现了。
堆中有足够的内存并且 calloc() 没有 return 一个 NULL 指针，这可能是依赖于实现的吗？我使用的是 TI ARM 编译器和 Code Composer Studio，而不是 gcc。
也许我遗漏了什么，所以我会继续寻找。谢谢你的时间。
编辑1：
这是上面代码的输出，可以正常工作。
>>>> Begin program.
Size of uint8_t: 1 bytes.
Size of uint16_t: 2 bytes.
Size of uint32_t: 4 bytes.
Size of uint64_t: 8 bytes.
Size of fSpi_Mod*: 8 bytes.
Size of fSpi_Mod: 24 bytes.
Size of fGpio_Pin**: 8 bytes.
Size of fGpio_Pin*: 8 bytes.
Size of fGpio_Pin: 8 bytes.
----
The address of the structure is 0x1DF7010.
The value of mode is 0x5 and address 0x1DF7010.
The value of nPins is 0x4 and address 0x1DF7014.
The value of Pins is 0x1DF7030 and address 0x1DF7018.
#0 | The pointer that points to Gpio structure is 0x1DF7060 at address 0x1DF7030.
#0 | The value of Pin of Gpio structure is 0x0 and address 0x1DF7060.
#0 | The value of Port of Gpio structure is 0x0 and address 0x1DF7064.
#1 | The pointer that points to Gpio structure is 0x1DF7080 at address 0x1DF7038.
#1 | The value of Pin of Gpio structure is 0x0 and address 0x1DF7080.
#1 | The value of Port of Gpio structure is 0x0 and address 0x1DF7084.
#2 | The pointer that points to Gpio structure is 0x1DF70A0 at address 0x1DF7040.
#2 | The value of Pin of Gpio structure is 0x0 and address 0x1DF70A0.
#2 | The value of Port of Gpio structure is 0x0 and address 0x1DF70A4.
#3 | The pointer that points to Gpio structure is 0x1DF70C0 at address 0x1DF7048.
#3 | The value of Pin of Gpio structure is 0x0 and address 0x1DF70C0.
#3 | The value of Port of Gpio structure is 0x0 and address 0x1DF70C4.
----
>>>> End program.
在我的应用程序中（我不能 post 图片我没有足够的声誉）：
调用后：
我认为您的第一个 calloc 调用分配的内存不足。从您发布的调试器的屏幕截图：
SpiRfid = (fSpi_Mod*) calloc(1, sizeof(SpiRfid));
这只会为指针分配足够的内存，而不是结构。你可能想要
SpiRfid = (fSpi_Mod*) calloc(1, sizeof(*SpiRfid));
如图所示，Matthew Wightman 指出，第一个 calloc 不正确，特别是 sizeof 运算符。图像中的 sizeof 运算符分配 space 用于指向 fSpi_Mod 结构的指针类型的指针（SpiRfid 是此类变量），我的意图是分配 space 用于 fSpi_Mod结构。这是我的错字。
因此，改变这个：
sizeof(SpiRfid)
为此：
sizeof(fSpi_Mod)
成功了。这只是一种可能的解决方案。
我在 Tiva C launchpad (ARM Cortex M4) 上分配内存时遇到问题，我想做的是在某个时候动态分配指向另一个结构内部结构的指针 calloc() returns 一个指针，其值与存储指针的地址相同。
我觉得这有点难以解释，所以我编写了这段代码来说明我想做的事情并且在 here 上运行得很好，但在我的应用程序中它的运行方式不同.
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <stddef.h>
typedef struct
{
uint32_t Pin;
uint32_t Port;
} fGpio_Pin;
typedef struct
{
uint32_t Mode;
uint32_t nPins;
fGpio_Pin** Pins;
} fSpi_Mod;
fSpi_Mod* Spi;
void printSizes (void)
{
printf("Size of uint8_t: %i bytes.\n", sizeof(uint8_t));
printf("Size of uint16_t: %i bytes.\n", sizeof(uint16_t));
printf("Size of uint32_t: %i bytes.\n", sizeof(uint32_t));
printf("Size of uint64_t: %i bytes.\n", sizeof(uint64_t));
printf("Size of fSpi_Mod*: %i bytes.\n", sizeof(fSpi_Mod*));
printf("Size of fSpi_Mod: %i bytes.\n", sizeof(fSpi_Mod));
printf("Size of fGpio_Pin**: %i bytes.\n", sizeof(fGpio_Pin**));
printf("Size of fGpio_Pin*: %i bytes.\n", sizeof(fGpio_Pin*));
printf("Size of fGpio_Pin: %i bytes.\n", sizeof(fGpio_Pin));
printf("----\n");
}
void printStructure (fSpi_Mod* Spi_Mod)
{
uint8_t i;
printf("The address of the structure is 0x%X.\n", Spi_Mod);
printf("The value of mode is 0x%X and address 0x%X.\n", Spi_Mod->Mode, &(Spi_Mod->Mode));
printf("The value of nPins is 0x%X and address 0x%X.\n", Spi_Mod->nPins, &(Spi_Mod->nPins));
printf("The value of Pins is 0x%X and address 0x%X.\n", Spi_Mod->Pins, &(Spi_Mod->Pins));
for (i = 0; i < Spi_Mod->nPins; i++)
{
printf("#%i | The pointer that points to Gpio structure is 0x%X at address 0x%X.\n", i, *(Spi_Mod->Pins + i), &(*(Spi_Mod->Pins + i)));
printf("#%i | The value of Pin of Gpio structure is 0x%X and address 0x%X.\n", i, ((*(Spi_Mod->Pins + i)))->Pin, &(((*(Spi_Mod->Pins + i)))->Pin));
printf("#%i | The value of Port of Gpio structure is 0x%X and address 0x%X.\n", i, ((*(Spi_Mod->Pins + i)))->Port, &(((*(Spi_Mod->Pins + i)))->Port));
}
printf("----\n");
}
int main()
{
uint8_t i = 0;
printf(">>>> Begin program.\n");
printSizes();
Spi = (fSpi_Mod*) calloc(1, sizeof(fSpi_Mod));
if (Spi == NULL) {
printf("Insufficient memory.\n");
return 1;
}
//printStructure(Spi);
Spi->Mode = 0x05;
Spi->nPins = 0x04;
Spi->Pins = (fGpio_Pin**) calloc(Spi->nPins, sizeof(fGpio_Pin*));
if (Spi->Pins == NULL)
{
printf("Insufficient memory.\n");
return 1;
}
//printStructure(Spi);
for (i = 0; i < Spi->nPins; i++)
{
(*(Spi->Pins + i)) = (fGpio_Pin*) calloc(1, sizeof(fGpio_Pin));
if ((*(Spi->Pins + i)) == NULL)
{
printf("Insufficient memory.\n");
return 1;
}
}
printStructure(Spi);
printf(">>>> End program.\n");
}
在我的应用程序中，当我尝试分配四个 "pointer to (fGpio_Pin*)" 类型的指针并将其转换为 (fGpio_Pin**) 时，calloc() returns [=17 的地址=]，所以基本上Spi->Pins的地址和它的值是一样的，就变成了指向它自己的指针，这时候问题就开始出现了。
堆中有足够的内存并且 calloc() 没有 return 一个 NULL 指针，这可能是依赖于实现的吗？我使用的是 TI ARM 编译器和 Code Composer Studio，而不是 gcc。
也许我遗漏了什么，所以我会继续寻找。谢谢你的时间。
编辑1：
这是上面代码的输出，可以正常工作。
>>>> Begin program.
Size of uint8_t: 1 bytes.
Size of uint16_t: 2 bytes.
Size of uint32_t: 4 bytes.
Size of uint64_t: 8 bytes.
Size of fSpi_Mod*: 8 bytes.
Size of fSpi_Mod: 24 bytes.
Size of fGpio_Pin**: 8 bytes.
Size of fGpio_Pin*: 8 bytes.
Size of fGpio_Pin: 8 bytes.
----
The address of the structure is 0x1DF7010.
The value of mode is 0x5 and address 0x1DF7010.
The value of nPins is 0x4 and address 0x1DF7014.
The value of Pins is 0x1DF7030 and address 0x1DF7018.
#0 | The pointer that points to Gpio structure is 0x1DF7060 at address 0x1DF7030.
#0 | The value of Pin of Gpio structure is 0x0 and address 0x1DF7060.
#0 | The value of Port of Gpio structure is 0x0 and address 0x1DF7064.
#1 | The pointer that points to Gpio structure is 0x1DF7080 at address 0x1DF7038.
#1 | The value of Pin of Gpio structure is 0x0 and address 0x1DF7080.
#1 | The value of Port of Gpio structure is 0x0 and address 0x1DF7084.
#2 | The pointer that points to Gpio structure is 0x1DF70A0 at address 0x1DF7040.
#2 | The value of Pin of Gpio structure is 0x0 and address 0x1DF70A0.
#2 | The value of Port of Gpio structure is 0x0 and address 0x1DF70A4.
#3 | The pointer that points to Gpio structure is 0x1DF70C0 at address 0x1DF7048.
#3 | The value of Pin of Gpio structure is 0x0 and address 0x1DF70C0.
#3 | The value of Port of Gpio structure is 0x0 and address 0x1DF70C4.
----
>>>> End program.
在我的应用程序中（我不能 post 图片我没有足够的声誉）：
调用后：
我认为您的第一个 calloc 调用分配的内存不足。从您发布的调试器的屏幕截图：
SpiRfid = (fSpi_Mod*) calloc(1, sizeof(SpiRfid));
这只会为指针分配足够的内存，而不是结构。你可能想要
SpiRfid = (fSpi_Mod*) calloc(1, sizeof(*SpiRfid));
如图所示，Matthew Wightman 指出，第一个 calloc 不正确，特别是 sizeof 运算符。图像中的 sizeof 运算符分配 space 用于指向 fSpi_Mod 结构的指针类型的指针（SpiRfid 是此类变量），我的意图是分配 space 用于 fSpi_Mod结构。这是我的错字。
因此，改变这个：
sizeof(SpiRfid)
为此：
sizeof(fSpi_Mod)
成功了。这只是一种可能的解决方案。