[v3,32/54] tests/qtest: libqtest: Adapt global_qtest declaration for win32

Commit Message

Bin Meng Sept. 25, 2022, 11:30 a.m. UTC

From: Xuzhou Cheng <[e-mail]>

Commit dd2107497275 ("tests/libqtest: Use libqtest-single.h in tests that require global_qtest")
moved global_qtest to libqtest-single.h, by declaring global_qtest
attribute to be common and weak.

This trick unfortunately does not work on Windows, and building
qtest test cases results in multiple definition errors of the weak
symbol global_qtest, as Windows PE does not have the concept of
the so-called weak symbol like ELF in the *nix world.

However Windows does provide a trick to declare a variable to be
a common symbol, via __declspec(selectany) [1]. It does not provide
the "strong override weak" effect but we don't need it in our use
case anyway. So let's use it for win32.

[1] https://docs.microsoft.com/en-us/cpp/cpp/selectany

Signed-off-by: Xuzhou Cheng <[e-mail]>
Signed-off-by: Bin Meng <[e-mail]>
---

(no changes since v2)

Changes in v2:
- Use __declspec(selectany) for the common weak symbol on Windows

 tests/qtest/libqtest-single.h | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Thomas Huth Sept. 26, 2022, 4:07 p.m. UTC | #1

On 25/09/2022 13.30, Bin Meng wrote:
> From: Xuzhou Cheng <[e-mail]>
> 
> Commit dd2107497275 ("tests/libqtest: Use libqtest-single.h in tests that require global_qtest")
> moved global_qtest to libqtest-single.h, by declaring global_qtest
> attribute to be common and weak.
> 
> This trick unfortunately does not work on Windows, and building
> qtest test cases results in multiple definition errors of the weak
> symbol global_qtest, as Windows PE does not have the concept of
> the so-called weak symbol like ELF in the *nix world.
> 
> However Windows does provide a trick to declare a variable to be
> a common symbol, via __declspec(selectany) [1]. It does not provide
> the "strong override weak" effect but we don't need it in our use
> case anyway. So let's use it for win32.
> 
> [1] https://docs.microsoft.com/en-us/cpp/cpp/selectany
> 
> Signed-off-by: Xuzhou Cheng <[e-mail]>
> Signed-off-by: Bin Meng <[e-mail]>
> ---
> 
> (no changes since v2)
> 
> Changes in v2:
> - Use __declspec(selectany) for the common weak symbol on Windows
> 
>   tests/qtest/libqtest-single.h | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/tests/qtest/libqtest-single.h b/tests/qtest/libqtest-single.h
> index 4e7d0ae1dc..851724cbcb 100644
> --- a/tests/qtest/libqtest-single.h
> +++ b/tests/qtest/libqtest-single.h
> @@ -13,7 +13,11 @@
>   
>   #include "libqtest.h"
>   
> +#ifndef _WIN32
>   QTestState *global_qtest __attribute__((common, weak));
> +#else
> +__declspec(selectany) QTestState *global_qtest;
> +#endif
>   
>   /**
>    * qtest_start:

Good to know that it works also on Windows somehow!

Reviewed-by: Thomas Huth <[e-mail]>

Patch

diff --git a/tests/qtest/libqtest-single.h b/tests/qtest/libqtest-single.h
index 4e7d0ae1dc..851724cbcb 100644
--- a/tests/qtest/libqtest-single.h
+++ b/tests/qtest/libqtest-single.h
@@ -13,7 +13,11 @@ 
 
 #include "libqtest.h"
 
+#ifndef _WIN32
 QTestState *global_qtest __attribute__((common, weak));
+#else
+__declspec(selectany) QTestState *global_qtest;
+#endif
 
 /**
  * qtest_start: