1. keil安装不安装v5编译器，但又有一些项目需要

2. 在官网下载legacy compiler需要注册账号

3.下载windows上面的是一个安装包，它喜欢安装到program files(x86)里面，会导致编译的时候即使项目设置里面设置好了编译器的位置，编译器也找不到license，出现以下报错

Error: C9555E: Failed to check out a license.

The license file could not be found. Check that ARMLMD_LICENSE_FILE is set correctly.

ARMLMD_LICENSE_FILE is not set. You must set this to the path to your license.

Information about this error is available at: http://ds.arm.com/support/lic87/m1

General licensing information is available at: http://ds.arm.com/support/licensing/

If you need further help, provide this complete error report to your supplier or license.support@arm.com.

- ARMLMD_LICENSE_FILE: unset

- LM_LICENSE_FILE: unset

- ARM_TOOL_VARIANT: unset

- ARM_PRODUCT_PATH: unset

- Product location: D:\Program Files (x86)\ARM_Compiler_5.06u7\sw\mappings

- Toolchain location: D:\Program Files (x86)\ARM_Compiler_5.06u7\Bin

- Selected tool variant: product

- Checkout feature: compiler5

- Feature version: 5.0202006

- Flex error code: -1

Product: ARM Compiler 5.06

Component: ARM Compiler 5.06 update 7 (build 960)

Tool: ArmCC [4d365d]

"..\Output\STM32F103C8T6.axf" - 45 Error(s), 0 Warning(s).

Target not created.

Build Time Elapsed: 00:00:03

正确做法是按照v5编译器的时候安装到keil安装时指定的安装目录里面的ARMCLANG同一个位置。这样编译器就知道license在哪里了。

感谢gemini老师。