Re: [PATCH v2 2/4] config: drop file pointer validity check in get_next_char()
On Sun, Mar 10, 2013 at 05:58:57PM +0100, Heiko Voigt wrote:
The only location where cf is set in this file is in do_config_from().
This function has only one callsite which is config_from_file(). In
config_from_file() its ensured that the f member is set to non-zero.
[...]
- if (cf ((f = cf-f) != NULL)) {
+ if (cf) {
I still think we can drop this conditional entirely. The complete call
graph looks like:
git_config_from_file
- git_parse_file
- get_next_char
- get_value
- get_next_char
- parse_value
- get_next_char
- get_base_var
- get_next_char
- get_extended_base_var
- get_next_char
That is, every path to get_next_char happens while we are in
git_config_from_file, and that function guarantees that cf = top, and
that top.f != NULL. We do not have to even do any analysis of the
conditions for each call, because we never change cf nor top.f
except when we set them in git_config_from_file.
-Peff
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Re: [PATCH v2 2/4] config: drop file pointer validity check in get_next_char()
On Tue, Mar 12, 2013 at 07:00:03AM -0400, Jeff King wrote:
On Sun, Mar 10, 2013 at 05:58:57PM +0100, Heiko Voigt wrote:
The only location where cf is set in this file is in do_config_from().
This function has only one callsite which is config_from_file(). In
config_from_file() its ensured that the f member is set to non-zero.
[...]
- if (cf ((f = cf-f) != NULL)) {
+ if (cf) {
I still think we can drop this conditional entirely. The complete call
graph looks like:
git_config_from_file
- git_parse_file
- get_next_char
- get_value
- get_next_char
- parse_value
- get_next_char
- get_base_var
- get_next_char
- get_extended_base_var
- get_next_char
That is, every path to get_next_char happens while we are in
git_config_from_file, and that function guarantees that cf = top, and
that top.f != NULL. We do not have to even do any analysis of the
conditions for each call, because we never change cf nor top.f
except when we set them in git_config_from_file.
Ok if you say so I will do that :-). I was thinking about adding a patch
that would remove cf as a global variable and explicitely pass it down
to get_next_char. That makes it more obvious that it actually is != NULL.
Looking at your callgraph I do not think its that much work. What do you
think?
BTW, how did you generate this callgraph? Do you have a nice tool for that?
Cheers Heiko
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Re: [PATCH v2 2/4] config: drop file pointer validity check in get_next_char()
On Tue, Mar 12, 2013 at 05:00:56PM +0100, Heiko Voigt wrote:
On Tue, Mar 12, 2013 at 07:00:03AM -0400, Jeff King wrote:
On Sun, Mar 10, 2013 at 05:58:57PM +0100, Heiko Voigt wrote:
The only location where cf is set in this file is in do_config_from().
This function has only one callsite which is config_from_file(). In
config_from_file() its ensured that the f member is set to non-zero.
[...]
- if (cf ((f = cf-f) != NULL)) {
+ if (cf) {
I still think we can drop this conditional entirely. The complete call
graph looks like:
git_config_from_file
- git_parse_file
- get_next_char
- get_value
- get_next_char
- parse_value
- get_next_char
- get_base_var
- get_next_char
- get_extended_base_var
- get_next_char
That is, every path to get_next_char happens while we are in
git_config_from_file, and that function guarantees that cf = top, and
that top.f != NULL. We do not have to even do any analysis of the
conditions for each call, because we never change cf nor top.f
except when we set them in git_config_from_file.
Ok if you say so I will do that :-). I was thinking about adding a patch
that would remove cf as a global variable and explicitely pass it down
to get_next_char. That makes it more obvious that it actually is != NULL.
Looking at your callgraph I do not think its that much work. What do you
think?
I just had a look and unfortunately there are other functions that use
this variable (namely handle_path_include) for which its not that easy
to pass this in. So I will just drop the check here.
Cheers Heiko
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Re: [PATCH v2 2/4] config: drop file pointer validity check in get_next_char()
On Tue, Mar 12, 2013 at 05:00:56PM +0100, Heiko Voigt wrote: That is, every path to get_next_char happens while we are in git_config_from_file, and that function guarantees that cf = top, and that top.f != NULL. We do not have to even do any analysis of the conditions for each call, because we never change cf nor top.f except when we set them in git_config_from_file. Ok if you say so I will do that :-). I was thinking about adding a patch that would remove cf as a global variable and explicitely pass it down to get_next_char. That makes it more obvious that it actually is != NULL. Looking at your callgraph I do not think its that much work. What do you think? Yeah, I think that makes it more obvious what is going on, but you will run into trouble if you ever want that information to cross the void * boundary of a config callback, as adding a new parameter there is hard. The only place we do that now is for git_config_include, and I think you could get by with stuffing it into the config_include_data struct (which is already there to deal with this problem). It would also make something like this patch hard or impossible: http://article.gmane.org/gmane.comp.version-control.git/190267 as it wants to access cf from arbitrary callbacks. That is not a patch that is actively under consideration, but I had considered polishing it up at some point. BTW, how did you generate this callgraph? Do you have a nice tool for that? I just did it manually in vi, working backwards from every instance of get_next_char, as it is not that big a graph. I suspect something like cscope could make it easier, but I don't know of any tool that will build the graph automatically (it would not be that hard from the data cscope has, though, so I wouldn't be surprised if such a tool exists). -Peff -- To unsubscribe from this list: send the line unsubscribe git in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH v2 2/4] config: drop file pointer validity check in get_next_char()
The only location where cf is set in this file is in do_config_from().
This function has only one callsite which is config_from_file(). In
config_from_file() its ensured that the f member is set to non-zero.
Signed-off-by: Heiko Voigt hvo...@hvoigt.net
---
config.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/config.c b/config.c
index 2c299dc..f55c43d 100644
--- a/config.c
+++ b/config.c
@@ -169,10 +169,10 @@ int git_config_from_parameters(config_fn_t fn, void *data)
static int get_next_char(void)
{
int c;
- FILE *f;
c = '\n';
- if (cf ((f = cf-f) != NULL)) {
+ if (cf) {
+ FILE *f = cf-f;
c = fgetc(f);
if (c == '\r') {
/* DOS like systems */
--
1.8.2.rc0.26.gf7384c5
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