[newlib-cygwin/cygwin-3_5-branch] Cygwin: pthread: Correct pthread_cleanup macros to avoid potential syntax errors

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=9dad29c238bfce017f54915b90a1c2c4fcac9529

commit 9dad29c238bfce017f54915b90a1c2c4fcac9529
Author:     Shaobo Song <shnusongshaobo@gmail.com>
AuthorDate: Sun Nov 10 12:15:04 2024 +0800
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Mon Nov 11 13:36:42 2024 +0100

    Cygwin: pthread: Correct pthread_cleanup macros to avoid potential syntax errors
    
    This commit revises `pthread_cleanup_push` and `pthread_cleanup_pop`
    macros to use a `do { ... } while(0)` wrapper, preventing syntax errors
    when used in certain contexts. The original code could fail when they
    are wrapped within a `do { ... } while(0)`, causing unintended behavior
    or compilation issues.
    
    Example of error:
    
      #include <pthread.h>
    
      #define pthread_cleanup_push_wrapper(_fn, _arg) do { \
        pthread_cleanup_push(_fn, _arg); \
      } while (0)
    
      #define pthread_cleanup_pop_wrapper(_execute) do { \
        pthread_cleanup_pop(_execute); \
      } while (0)
    
      void cleanup_fn (void *arg) {}
    
      void *thread_func (void *arg)
      {
        pthread_cleanup_push_wrapper(cleanup_fn, NULL);
        pthread_cleanup_pop_wrapper(1);
        return NULL;
      }
    
      int main (int argc, char **argv) {
        pthread_t thread_id;
        pthread_create(&thread_id, NULL, thread_func, NULL);
      }
    
    This would fail due to unmatched braces in the macro expansion. The new
    structure ensures the macro expands correctly in all cases.
    
    Fixes: 007276b30e0a ("* cygwin.din: Add _pthread_cleanup_push and _pthread_cleanup_pop.")
    Signed-off-by: Shaobo Song <shnusongshaobo@gmail.com>

Diff:
---
 winsup/cygwin/include/pthread.h | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/include/pthread.h b/winsup/cygwin/include/pthread.h
index 66d367d62265..cf2fcb04b3e2 100644
--- a/winsup/cygwin/include/pthread.h
+++ b/winsup/cygwin/include/pthread.h
@@ -110,10 +110,13 @@ typedef struct _pthread_cleanup_handler
 void _pthread_cleanup_push (__pthread_cleanup_handler *handler);
 void _pthread_cleanup_pop (int execute);
 
-#define pthread_cleanup_push(_fn, _arg) { __pthread_cleanup_handler __cleanup_handler = \
-					 { _fn, _arg, NULL }; \
-					 _pthread_cleanup_push( &__cleanup_handler );
-#define pthread_cleanup_pop(_execute) _pthread_cleanup_pop( _execute ); }
+#define pthread_cleanup_push(_fn, _arg) \
+  do { \
+    __pthread_cleanup_handler __cleanup_handler = { _fn, _arg, NULL }; \
+    _pthread_cleanup_push(&__cleanup_handler)
+#define pthread_cleanup_pop(_execute) \
+    _pthread_cleanup_pop(_execute); \
+  } while (0)
 
 /* Condition variables */
 int pthread_cond_broadcast (pthread_cond_t *);