cmake: fix EXTRAVERSION regex

[arnopo]

Use '\' instead of '' for the regex argument described in cmake specification:
The quoted argument "\(\a\+b\)" specifies a regex that matches the exact string (a+b). Each \ is parsed in a quoted argument as just , so the regex itself is actually (\a+\b).

This fixes build error reported in OpenAMP CI

CMake Error at zephyrproject/zephyr/cmake/modules/version.cmake:66 (string):
Syntax error in cmake code at

zephyrproject/zephyr/cmake/modules/version.cmake:66

when parsing string

EXTRAVERSION = ([a-z0-9.-]*)

Invalid escape sequence .
Call Stack (most recent call first):
zephyrproject/zephyr/share/zephyr-package/cmake/ZephyrConfigVersion.cmake:59 (include)
cmake/syscheck.cmake:8 (find_package)
CMakeLists.txt:17 (include)

[tejlmand]

LGTM, though the final - doesn't need escaping, but does no harm neither.

[tejlmand]

just a small observation.
When - is placed at the end of matching brackets, [, ], then it doesn't need to be escaped.

Ref:

To match a literal - using brackets, make it the first or the last character, e.g., [+*/-] matches basic mathematical operators.

Suggested change

	string(REGEX MATCH "EXTRAVERSION = ([a-z0-9\\.\\-]*)" _ ${ver})
	string(REGEX MATCH "EXTRAVERSION = ([a-z0-9\\.-]*)" _ ${ver})

[tejlmand]

The use of \\ actually matches a literal \, resulting in \ to become a valid char in the VERSION file.

For example using:

# VERSION File content
...
EXTRAVERSION = 4.5\-5

results in:

Loading Zephyr default modules (Zephyr repository).
...
-- Zephyr version: 4.0.99-4.5\-5 (/projects/github/review/zephyr)

which again causes issues later when Zephyr's VERSION is processed using \.

[tejlmand]

The use of \\. (and \\-) actually means the regex matches a literal \, which is not what we want.

The reason for the error:

CMake Error at zephyrproject/zephyr/cmake/modules/version.cmake:66 (string):
Syntax error in cmake code at

zephyrproject/zephyr/cmake/modules/version.cmake:66

when parsing string

EXTRAVERSION = ([a-z0-9.-]*)

Invalid escape sequence .

is due to CMP0053 using old policy.
The use of old policy is due to the use of CMake minimum version 3.0.2 here:
https://github.com/OpenAMP/libmetal/blob/465fcf018c760785fc04fcd90a72b17ab9a8a58d/CMakeLists.txt#L1

Please note that Zephyr requires CMake version >=3.20.

This error caused by old CMake version required can also be verified with the following CMake snippet:

# test.cmake
cmake_minimum_required(VERSION 3.20)

string(REGEX MATCH "EXTRAVERSION = ([a-z0-9\.-]*)" _ "EXTRAVERSION = 4.5-5")
message("Match: ${CMAKE_MATCH_1}")

prints:

$ cmake -P test.cmake
Match: 4.5-5

but:

# test.cmake
cmake_minimum_required(VERSION 3.0.2)

string(REGEX MATCH "EXTRAVERSION = ([a-z0-9\.-]*)" _ "EXTRAVERSION = 4.5-5")
message("Match: ${CMAKE_MATCH_1}")

prints:

$ cmake -P test.cmake
CMake Error at test.cmake:4 (string):
  Syntax error in cmake code at

    /tmp/cmake/regex.cmake:4

  when parsing string

    EXTRAVERSION = ([a-z0-9\.-]*)

  Invalid escape sequence \.

Same error is seen when setting CMP0053 policy to old.

[tejlmand]

The use of \\ actually matches a literal \, resulting in \ to become a valid char in the VERSION file.

For example using:

# VERSION File content
...
EXTRAVERSION = 4.5\-5

results in:

Loading Zephyr default modules (Zephyr repository).
...
-- Zephyr version: 4.0.99-4.5\-5 (/projects/github/review/zephyr)

which again causes issues later when Zephyr's VERSION is processed using \.

[arnopo]

Thanks @tejlmand for your deep analysis!

I will fix that in OpenAMP.

I will close this one except if you want that i sent the non mandatory fix for the '-'