refs: print errno for read_raw_ref if GIT_TRACE_REFS is set

PATCH Superseded Han-Wen Nienhuys via GitGitGadget 3 participants 7 messages Apr 12, 2021 – Apr 23, 2021

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Han-Wen Nienhuys via GitGitGadget

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2021-04-12 19:32 UTC #0 lore raw

PATCH 1/1 refs: print errno for read_raw_ref if GIT_TRACE_REFS is set

From: Han-Wen Nienhuys <[email protected]>

The ref backend API uses errno as a sideband error channel.

Signed-off-by Han-Wen Nienhuys <[email protected]>

---
refs: print errno for read_raw_ref if GIT_TRACE_REFS is set

The ref backend API uses errno as a sideband error channel.

Signed-off-by Han-Wen Nienhuys [email protected]

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1002%2Fhanwen%2Ferrno-debug-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1002/hanwen/errno-debug-v1
Pull-Request: https://github.com/git/git/pull/1002

 refs/debug.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

refs/debug.c +4 -1

index 922e64fa6ad9..576bf98e74ae 100644
@@ -244,6 +244,7 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
 	int res = 0;
 
 	oidcpy(oid, &null_oid);
+	errno = 0;
 	res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
 					    type);

@@ -251,7 +252,9 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
 		trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
 			refname, oid_to_hex(oid), referent->buf, *type, res);
 	} else {
-		trace_printf_key(&trace_refs, "read_raw_ref: %s: %d\n", refname, res);
+		trace_printf_key(&trace_refs,
+				 "read_raw_ref: %s: %d (errno %d)\n", refname,
+				 res, errno);
 	}
 	return res;
 }

base-commit: 89b43f80a514aee58b662ad606e6352e03eaeee4

Signature · 1 line

gitgitgadget

Junio C Hamano

2021-04-12 21:45 UTC #1 lore raw

Quoted 13 lines · Han-Wen Nienhuys via GitGitGadget

refs/debug.c +1 -0

index 922e64fa6ad9..576bf98e74ae 100644
@@ -244,6 +244,7 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
 	int res = 0;
 
 	oidcpy(oid, &null_oid);
+	errno = 0;
 	res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
 					    type);

refs/debug.c static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname, · line 258

Quoted 8 lines

refs/debug.c +3 -1

@@ -251,7 +252,9 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
 		trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
 			refname, oid_to_hex(oid), referent->buf, *type, res);
 	} else {
-		trace_printf_key(&trace_refs, "read_raw_ref: %s: %d\n", refname, res);
+		trace_printf_key(&trace_refs,
+				 "read_raw_ref: %s: %d (errno %d)\n", refname,
+				 res, errno);
 	}

OK. Between trace_printf_key() and the return of the call to read_raw_ref() method of the ref backend is only an "if (res == 0)" condition and I do not see anything that might clobber errno.

I do wonder if we want strerror(errno) instead of the number, but I can go either way (it's just a trace output).

Thanks, will queue.

Han-Wen Nienhuys

2021-04-13 11:58 UTC #2 lore raw

Quoted 5 lines · Junio C Hamano

Quoted 5 lines

refs/debug.c +0 -1

@@ -251,7 +252,9 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
              trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
                      refname, oid_to_hex(oid), referent->buf, *type, res);
      } else {
-             trace_printf_key(&trace_refs, "read_raw_ref: %s: %d\n", refname, res);

Quoted 8 lines

refs/debug.c static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname, · line 258
Quoted 4 lines
refs/debug.c +3 -0
+             trace_printf_key(&trace_refs,
+                              "read_raw_ref: %s: %d (errno %d)\n", refname,
+                              res, errno);
      }
OK. Between trace_printf_key() and the return of the call to read_raw_ref() method of the ref backend is only an "if (res == 0)" condition and I do not see anything that might clobber errno.

I don't want to bet on that. Let me send a second round.

Quoted 2 lines

I do wonder if we want strerror(errno) instead of the number, but I can go either way (it's just a trace output).

For tracing, it would be most useful if we got the actual symbol (eg. ENOENT). Is there a way to get at that?

Signature · 11 lines

Han-Wen Nienhuys - Google Munich
I work 80%. Don't expect answers from me on Fridays.
--

Google Germany GmbH, Erika-Mann-Strasse 33, 80636 Munich

Registergericht und -nummer: Hamburg, HRB 86891

Sitz der Gesellschaft: Hamburg

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado

Han-Wen Nienhuys

2021-04-13 12:02 UTC #3 lore raw

Quoted 16 lines · Han-Wen Nienhuys

Quoted 5 lines · Junio C Hamano
Quoted 5 lines
refs/debug.c +0 -1
@@ -251,7 +252,9 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
              trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
                      refname, oid_to_hex(oid), referent->buf, *type, res);
      } else {
-             trace_printf_key(&trace_refs, "read_raw_ref: %s: %d\n", refname, res);
Quoted 8 lines
refs/debug.c static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname, · line 258
Quoted 4 lines
refs/debug.c +3 -0
+             trace_printf_key(&trace_refs,
+                              "read_raw_ref: %s: %d (errno %d)\n", refname,
+                              res, errno);
      }
OK. Between trace_printf_key() and the return of the call to read_raw_ref() method of the ref backend is only an "if (res == 0)" condition and I do not see anything that might clobber errno.

Quoted 1 line

I don't want to bet on that. Let me send a second round.

oh, ugh. In email, there are two calls, but one is prefixed with '-'.

Nevertheless, a bit of paranoia doesn't hurt here.

Signature · 11 lines

Han-Wen Nienhuys - Google Munich
I work 80%. Don't expect answers from me on Fridays.
--

Google Germany GmbH, Erika-Mann-Strasse 33, 80636 Munich

Registergericht und -nummer: Hamburg, HRB 86891

Sitz der Gesellschaft: Hamburg

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado

Junio C Hamano

2021-04-13 20:08 UTC #4 lore raw

In reply to Han-Wen Nienhuys

Quoted 5 lines · Han-Wen Nienhuys

Quoted 2 lines
I do wonder if we want strerror(errno) instead of the number, but I can go either way (it's just a trace output).
For tracing, it would be most useful if we got the actual symbol (eg. ENOENT). Is there a way to get at that?

I do not think there is.

And that is the reason why we see everywhere calls to die_errno(), error(..., strerror(errno)), etc.

As this is interpolated into trace with untranslated string, I suspect that strerror() is not a good match, so let's live with %d for now.

Thanks.

Han-Wen Nienhuys

2021-04-23 08:35 UTC #5 lore raw

Quoted 9 lines · Junio C Hamano

Quoted 5 lines · Han-Wen Nienhuys
Quoted 2 lines
I do wonder if we want strerror(errno) instead of the number, but I can go either way (it's just a trace output).
For tracing, it would be most useful if we got the actual symbol (eg. ENOENT). Is there a way to get at that?

Quoted 8 lines

I do not think there is.
And that is the reason why we see everywhere calls to die_errno(), error(..., strerror(errno)), etc.
As this is interpolated into trace with untranslated string, I suspect that strerror() is not a good match, so let's live with %d for now.

Great!

This topic is marked as

Waiting for reviews to conclude.
cf. <[email protected]>

but I don't know what is left to do. Oversight?

Signature · 7 lines

Han-Wen Nienhuys - Google Munich
I work 80%. Don't expect answers from me on Fridays.
--
Google Germany GmbH, Erika-Mann-Strasse 33, 80636 Munich
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado

Han-Wen Nienhuys via GitGitGadget

author

2021-04-13 12:10 UTC #6 lore raw

PATCH v2 1/1 refs: print errno for read_raw_ref if GIT_TRACE_REFS is set

In reply to Han-Wen Nienhuys via GitGitGadget

From: Han-Wen Nienhuys <[email protected]>

The ref backend API uses errno as a sideband error channel.

Signed-off-by Han-Wen Nienhuys <[email protected]>

---
refs: print errno for read_raw_ref if GIT_TRACE_REFS is set

The ref backend API uses errno as a sideband error channel.

Signed-off-by Han-Wen Nienhuys [email protected]

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1002%2Fhanwen%2Ferrno-debug-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1002/hanwen/errno-debug-v2
Pull-Request: https://github.com/git/git/pull/1002

Range-diff vs v1:

1: 9b150c5563f9 ! 1: 1e9a8990e7f2 refs: print errno for read_raw_ref if GIT_TRACE_REFS is set

     @@ Commit message
      
       ## refs/debug.c ##
      @@ refs/debug.c: static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
     + {
     + 	struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
       	int res = 0;
     ++	int saved_errno = 0;
       
       	oidcpy(oid, &null_oid);
      +	errno = 0;
       	res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
       					    type);
     ++	saved_errno = errno;
       
     -@@ refs/debug.c: static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
     + 	if (res == 0) {
       		trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
       			refname, oid_to_hex(oid), referent->buf, *type, res);
       	} else {
      -		trace_printf_key(&trace_refs, "read_raw_ref: %s: %d\n", refname, res);
      +		trace_printf_key(&trace_refs,
      +				 "read_raw_ref: %s: %d (errno %d)\n", refname,
     -+				 res, errno);
     ++				 res, saved_errno);
       	}
       	return res;
       }

 refs/debug.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

refs/debug.c +6 -1

index 922e64fa6ad9..286987b72166 100644
@@ -242,16 +242,21 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
 {
 	struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
 	int res = 0;
+	int saved_errno = 0;
 
 	oidcpy(oid, &null_oid);
+	errno = 0;
 	res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
 					    type);
+	saved_errno = errno;
 
 	if (res == 0) {
 		trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
 			refname, oid_to_hex(oid), referent->buf, *type, res);
 	} else {
-		trace_printf_key(&trace_refs, "read_raw_ref: %s: %d\n", refname, res);
+		trace_printf_key(&trace_refs,
+				 "read_raw_ref: %s: %d (errno %d)\n", refname,
+				 res, saved_errno);
 	}
 	return res;
 }

base-commit: 89b43f80a514aee58b662ad606e6352e03eaeee4

Signature · 1 line

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