[PATCH] Mark win32's pthread_exit() as NORETURN

The pthread_exit() function is not expected to return. Ever.

Pointed out by Jeff King.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/win32/pthread.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
index 20b35a2..148db60 100644
--- a/compat/win32/pthread.h
+++ b/compat/win32/pthread.h

@@ -78,7 +78,7 @@ extern int win32_pthread_join(pthread_t *thread, void **value_ptr);
 #define pthread_equal(t1, t2) ((t1).tid == (t2).tid)
 extern pthread_t pthread_self(void);
 
-static inline int pthread_exit(void *ret)
+static inline int NORETURN pthread_exit(void *ret)
 {
 	ExitThread((DWORD)(intptr_t)ret);
 }

-- 
2.7.2.windows.1.5.g64acc33

On Tue, Mar 01, 2016 at 02:53:04PM +0100, Johannes Schindelin wrote:

Looks obviously correct to me (I'll assume Windows isn't so crazy as to
let ExitThread ever return :) ).

-Peff

-- 
2.7.2.windows.1.5.g64acc33

Hi Peff,

On Tue, 1 Mar 2016, Jeff King wrote:

On Tue, Mar 01, 2016 at 02:53:04PM +0100, Johannes Schindelin wrote:

quoted

The pthread_exit() function is not expected to return. Ever.

Pointed out by Jeff King.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/win32/pthread.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
index 20b35a2..148db60 100644
--- a/compat/win32/pthread.h
+++ b/compat/win32/pthread.h

@@ -78,7 +78,7 @@ extern int win32_pthread_join(pthread_t *thread, void **value_ptr);
 #define pthread_equal(t1, t2) ((t1).tid == (t2).tid)
 extern pthread_t pthread_self(void);
 
-static inline int pthread_exit(void *ret)
+static inline int NORETURN pthread_exit(void *ret)
 {
 	ExitThread((DWORD)(intptr_t)ret);
 }

Looks obviously correct to me (I'll assume Windows isn't so crazy as to
let ExitThread ever return :) ).

Indeed, you are correct in your implicit assumption that I should have
clarified that in my commit message. I will amend the commit message.

Ciao,
Dscho

The pthread_exit() function is not expected to return. Ever. On Windows,
we call ExitThread() whose documentation claims: "This function does not
return a value.":

	https://msdn.microsoft.com/en-us/library/windows/desktop/ms682659

Pointed out by Jeff King.

Signed-off-by: Johannes Schindelin <redacted>
---

	Relative to v1, only the commit message changed (to clarify that
	ExitThread() indeed never returns).

 compat/win32/pthread.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
index 20b35a2..148db60 100644
--- a/compat/win32/pthread.h
+++ b/compat/win32/pthread.h

@@ -78,7 +78,7 @@ extern int win32_pthread_join(pthread_t *thread, void **value_ptr);
 #define pthread_equal(t1, t2) ((t1).tid == (t2).tid)
 extern pthread_t pthread_self(void);
 
-static inline int pthread_exit(void *ret)
+static inline int NORETURN pthread_exit(void *ret)
 {
 	ExitThread((DWORD)(intptr_t)ret);
 }

-- 
2.7.2.windows.1.5.g64acc33

Am 01.03.2016 um 15:13 schrieb Johannes Schindelin:

The pthread_exit() function is not expected to return. Ever. On Windows,
we call ExitThread() whose documentation claims: "This function does not
return a value.":

Does this really mean that ExitThread() does not return ?

Just wondering...

Stefan
-- 
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python -c "print '73746566616e2e6e616577654061746c61732d656c656b74726f6e696b2e636f6d'.decode('hex')" 
GPG Key fingerprint = 2DF5 E01B 09C3 7501 BCA9  9666 829B 49C5 9221 27AF

Am 01.03.2016 um 15:13 schrieb Johannes Schindelin:

The pthread_exit() function is not expected to return. Ever. On Windows,
we call ExitThread() whose documentation claims: "This function does not
return a value.":

	https://msdn.microsoft.com/en-us/library/windows/desktop/ms682659

This is misleading: MSDN marks all functions declared void as "does not 
return a value," for example, look at EnterCriticalSection:

https://msdn.microsoft.com/en-us/library/windows/desktop/ms682608

For this reason, I actually prefer your version 1 patch without the 
explanation.

I would have written it as

#ifdef __GNUC__
__attribute__((__noreturn__))
#endif
static inline int pthread_exit(void *ret) ...

but I can live with your version as long as it compiles.

Your solution is pragmatic: NORETURN is defined in git-compat-util.h, 
and by using it here, we depend on that pthread.h is included 
sufficiently late that the macro is available at this point. The 
instance in compat/nedmalloc/malloc.c.h is bracketed with #ifndef WIN32 
so that it is not compiled on Windows, all other instances are after 
git-compat-util.h or cache.h or in headers that are to be included only 
after git-compat-util.h or cache.h per convention. Looks like we are safe.

  {
  	ExitThread((DWORD)(intptr_t)ret);
  }

Hi,

On Tue, 1 Mar 2016, stefan.naewe@atlas-elektronik.com wrote:

Am 01.03.2016 um 15:13 schrieb Johannes Schindelin:

quoted

The pthread_exit() function is not expected to return. Ever. On Windows,
we call ExitThread() whose documentation claims: "This function does not
return a value.":

Does this really mean that ExitThread() does not return ?

I fixed the commit message in v3.

Thanks,
Dscho

The pthread_exit() function is not expected to return. Ever. On Windows,
we call ExitThread() whose documentation claims: "Ends the calling
thread", i.e. there is no condition in which this function simply
returns: https://msdn.microsoft.com/en-us/library/windows/desktop/ms682659

While at it, fix the return type to be void, as per
http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_exit.html

Pointed out by Jeff King, helped by Stefan Naewe, Junio Hamano &
Johannes Sixt.

Signed-off-by: Johannes Schindelin <redacted>
---
 compat/win32/pthread.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Interdiff vs v2:

 diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
 index 148db60..b6ed9e7 100644
 --- a/compat/win32/pthread.h
 +++ b/compat/win32/pthread.h
 @@ -78,7 +78,7 @@ extern int win32_pthread_join(pthread_t *thread, void **value_ptr);
  #define pthread_equal(t1, t2) ((t1).tid == (t2).tid)
  extern pthread_t pthread_self(void);
  
 -static inline int NORETURN pthread_exit(void *ret)
 +static inline void NORETURN pthread_exit(void *ret)
  {
  	ExitThread((DWORD)(intptr_t)ret);
  }

diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
index 20b35a2..b6ed9e7 100644
--- a/compat/win32/pthread.h
+++ b/compat/win32/pthread.h

@@ -78,7 +78,7 @@ extern int win32_pthread_join(pthread_t *thread, void **value_ptr);
 #define pthread_equal(t1, t2) ((t1).tid == (t2).tid)
 extern pthread_t pthread_self(void);
 
-static inline int pthread_exit(void *ret)
+static inline void NORETURN pthread_exit(void *ret)
 {
 	ExitThread((DWORD)(intptr_t)ret);
 }

-- 
2.7.2.windows.1.5.g64acc33