即使未使用STM32 gcc(arm-none-eabi-gcc)链接printf [英] STM32 gcc (arm-none-eabi-gcc) links printf even though it is not used

问题描述

我似乎无法弄清楚为什么某些printf库函数从libc_nano.a链接到我的代码中，即使我从不使用任何printf.它窃取了至少2K的宝贵闪存空间.我可以在链接器映射文件中看到_printf_i，_vfprintf_r，_vfiprintf_r等部分.

I can't seem to figure out why some printf library functions get linked into my code from libc_nano.a even though I never use any printf. It steals at least 2K of valuable flash memory space. I can see the sections _printf_i, _vfprintf_r, _vfiprintf_r, etc. in my linker map file.

我尝试了

• Wl，-排除库选项
• 链接描述文件中的EXCLUDE_FILE(..)

这些都不会使符号从地图文件中消失.

None of these make the symbols disappear from the map file..

我的gcc选项:

CFLAGS = -Og -Wall -g3 -Wdouble-promotion -mcpu=cortex-m0 -mthumb -fmessage-length=0 -ffunction-sections -mfloat-abi=soft -DUSE_HAL_DRIVER

LFLAGS = -mcpu=cortex-m0 -mthumb -mfloat-abi=soft -specs=nosys.specs -specs=nano.specs -Wl,--gc-sections 

arm-none-eabi-gcc.exe(用于ARM嵌入式处理器的GNU工具)5.2.1 20151202(再出租)[ARM/嵌入式5分支修订231848]版权 (C)2015 Free Software Foundation，Inc..这是免费软件；看到 复制条件的来源.没有保修；甚至没有 特定目的的适销性或适用性.

arm-none-eabi-gcc.exe (GNU Tools for ARM Embedded Processors) 5.2.1 20151202 (re lease) [ARM/embedded-5-branch revision 231848] Copyright (C) 2015 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

首先，为什么它们被链接? 有什么方法可以排除它们?

First of all, why do they get linked? Is there any method to exclude them?

推荐答案

告诉链接器以生成交叉引用:-Wl,--cref

Tell the linker to generate a cross reference: -Wl,--cref

-cref

--cref

输出交叉参考表.如果正在生成链接器映射文件，则将交叉引用表打印到映射文件. 否则，它将被打印在标准输出上.的格式 该表是故意简化的，因此可以很容易地由 脚本(如果需要).符号被打印出来，按名称排序.为了 每个符号都会给出文件名列表.如果定义了符号， 列出的第一个文件是定义的位置.剩余的 文件包含对该符号的引用.

Output a cross reference table. If a linker map file is being generated, the cross reference table is printed to the map file. Otherwise, it is printed on the standard output. The format of the table is intentionally simple, so that it may be easily processed by a script if necessary. The symbols are printed out, sorted by name. For each symbol, a list of file names is given. If the symbol is defined, the first file listed is the location of the definition. The remaining files contain references to the symbol.

寻找以打印符号之一开头的行及其下方的行.

Look for a line starting with one of the print symbols, and the lines below it.

grep -A5 _printf *.map

您将找到内部使用printf的库函数.

There you'll find the library function that uses printf internally.

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