[PATCH 0/1] sparse-checkout: use extern for global variables

[PATCH 0/1] sparse-checkout: use extern for global variables

[Derrick Stolee via GitGitGadget]

I noticed this issue when resolving conflicts with our VFS for Git-enabled
branch in microsoft/git.

When I moved the global for core.sparseCheckout along with creating the
global for core.sparseCheckoutCone, I dropped the "extern" by habit. (We are
dropping these from function declarations, usually.) However, this means
something different for variables, and could lead to bugs. I haven't found
any, but it's better to be safe, right?

Thanks, -Stolee

Derrick Stolee (1):
  sparse-checkout: use extern for global variables

 cache.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


base-commit: 99c33bed562b41de6ce9bd3fd561303d39645048
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-506%2Fderrickstolee%2Fsparse-extern-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-506/derrickstolee/sparse-extern-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/506
-- 
gitgitgadget

[PATCH 1/1] sparse-checkout: use extern for global variables

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <dstolee@microsoft.com>

When the core.sparseCheckoutCone config setting was added in
879321eb0b ("sparse-checkout: add 'cone' mode" 2019-11-21), the
variables storing the config values for core.sparseCheckout and
core.sparseCheckoutCone were rearranged in cache.h, but in doing
so the "extern" keyword was dropped.

While we are tending to drop the "extern" keyword for function
declarations, it is still necessary for global variables used
across multiple *.c files. The impact of not having the extern
keyword may be unpredictable.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 cache.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/cache.h b/cache.h
index 1554488d66..cbfaead23a 100644
--- a/cache.h
+++ b/cache.h
@@ -958,8 +958,8 @@ extern int protect_hfs;
 extern int protect_ntfs;
 extern const char *core_fsmonitor;
 
-int core_apply_sparse_checkout;
-int core_sparse_checkout_cone;
+extern int core_apply_sparse_checkout;
+extern int core_sparse_checkout_cone;
 
 /*
  * Include broken refs in all ref iterations, which will
-- 
gitgitgadget

Re: [PATCH 1/1] sparse-checkout: use extern for global variables

[Junio C Hamano]

"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Derrick Stolee <dstolee@microsoft.com>
>
> When the core.sparseCheckoutCone config setting was added in
> 879321eb0b ("sparse-checkout: add 'cone' mode" 2019-11-21), the
> variables storing the config values for core.sparseCheckout and
> core.sparseCheckoutCone were rearranged in cache.h, but in doing
> so the "extern" keyword was dropped.
>
> While we are tending to drop the "extern" keyword for function
> declarations, it is still necessary for global variables used
> across multiple *.c files. The impact of not having the extern
> keyword may be unpredictable.

"May be unpredictable" might be a bit too strong, but I agree that
it is better not to rely on the "common extension" these days, and
instead make sure variable decls have "extern" in front.

Will queue.  Thanks.

> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>  cache.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/cache.h b/cache.h
> index 1554488d66..cbfaead23a 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -958,8 +958,8 @@ extern int protect_hfs;
>  extern int protect_ntfs;
>  extern const char *core_fsmonitor;
>  
> -int core_apply_sparse_checkout;
> -int core_sparse_checkout_cone;
> +extern int core_apply_sparse_checkout;
> +extern int core_sparse_checkout_cone;
>  
>  /*
>   * Include broken refs in all ref iterations, which will