[PATCH 1/7] ui-blob.c: Use a context structure in walk_tree()

[John Keeping]

On Sun, Mar 03, 2013 at 09:33:36PM +0100, Ferry Huberts wrote:
> 
> 
> On 03/03/13 21:25, John Keeping wrote:
> > On Sun, Mar 03, 2013 at 08:56:18PM +0100, Ferry Huberts wrote:
> >>
> >>
> >> On 03/03/13 18:06, Lukas Fleischer wrote:
> >>> Do not misuse global variables to save the context. Instead, use the
> >>> context pointer which was designed to share information between a
> >>> read_tree_fn and the caller.
> >>>
> >>> This also prevents from potential misuse of the global pointers
> >>> match_path and matched_sha1 after the referenced values have been
> >>> overwritten on the stack.
> >>>
> >>> Signed-off-by: Lukas Fleischer <cgit at cryptocrack.de>
> >>> ---
> >>>    ui-blob.c | 42 ++++++++++++++++++++++++++----------------
> >>>    1 file changed, 26 insertions(+), 16 deletions(-)
> >>>
> >>> diff --git a/ui-blob.c b/ui-blob.c
> >>> index 3d07ce5..4bcbc82 100644
> >>> --- a/ui-blob.c
> >>> +++ b/ui-blob.c
> >>> @@ -11,17 +11,22 @@
> >>>    #include "html.h"
> >>>    #include "ui-shared.h"
> >>>
> >>> -static char *match_path;
> >>> -static unsigned char *matched_sha1;
> >>> -static int found_path;
> >>> +struct walk_tree_context {
> >>> +	char *match_path;
> >>> +	unsigned char *matched_sha1;
> >>> +	int found_path;
> >>> +};
> >>>
> >>>    static int walk_tree(const unsigned char *sha1, const char *base, int baselen,
> >>> -	const char *pathname, unsigned mode, int stage, void *cbdata) {
> >>> -	if(strncmp(base, match_path, baselen)
> >>> -		|| strcmp(match_path + baselen, pathname))
> >>> +	const char *pathname, unsigned mode, int stage, void *cbdata)
> >>> +{
> >>> +	struct walk_tree_context *walk_tree_ctx = cbdata;
> >>> +
> >>> +	if(strncmp(base, walk_tree_ctx->match_path, baselen)
> >>> +		|| strcmp(walk_tree_ctx->match_path + baselen, pathname))
> >>>    		return READ_TREE_RECURSIVE;
> >>> -	memmove(matched_sha1, sha1, 20);
> >>> -	found_path = 1;
> >>> +	memmove(walk_tree_ctx->matched_sha1, sha1, 20);
> >>> +	walk_tree_ctx->found_path = 1;
> >>>    	return 0;
> >>>    }
> >>>
> >>> @@ -33,16 +38,19 @@ int cgit_print_file(char *path, const char *head)
> >>>    	unsigned long size;
> >>>    	struct commit *commit;
> >>>    	const char *paths[] = {path, NULL};
> >>> +	struct walk_tree_context walk_tree_ctx = {
> >>> +		.match_path = path,
> >>> +		.matched_sha1 = sha1,
> >>> +		.found_path = 0
> >>> +	};
> >>> +
> >>>    	if (get_sha1(head, sha1))
> >>>    		return -1;
> >>>    	type = sha1_object_info(sha1, &size);
> >>>    	if(type == OBJ_COMMIT && path) {
> >>>    		commit = lookup_commit_reference(sha1);
> >>> -		match_path = path;
> >>> -		matched_sha1 = sha1;
> >>> -		found_path = 0;
> >>> -		read_tree_recursive(commit->tree, "", 0, 0, paths, walk_tree, NULL);
> >>> -		if (!found_path)
> >>> +		read_tree_recursive(commit->tree, "", 0, 0, paths, walk_tree, &walk_tree_ctx);
> >>> +		if (!walk_tree_ctx.found_path)
> >>>    			return -1;
> >>>    		type = sha1_object_info(sha1, &size);
> >>>    	}
> >>> @@ -64,6 +72,10 @@ void cgit_print_blob(const char *hex, char *path, const char *head)
> >>>    	unsigned long size;
> >>>    	struct commit *commit;
> >>>    	const char *paths[] = {path, NULL};
> >>> +	struct walk_tree_context walk_tree_ctx = {
> >>> +		.match_path = path,
> >>> +		.matched_sha1 = sha1,
> >>
> >> forgot to initialise found_path
> >
> > Unnecessary - C99 6.7.8:
> >
> >      If there are fewer initializers in a brace-enclosed list than there
> >      are elements or members of an aggregate, or fewer characters in a
> >      string literal used to initialize an array of known size than there
> >      are elements in the array, the remainder of the aggregate shall be
> >      initialized implicitly the same as objects that have static storage
> >      duration.
> 
> which is what? zero?

Yes:

    If an object that has static storage duration is not initialized
    explicitly, then:
    — if it has pointer type, it is initialized to a null pointer;
    — if it has arithmetic type, it is initialized to (positive or
      unsigned) zero;
    — if it is an aggregate, every member is initialized (recursively)
      according to these rules;
    — if it is a union, the first named member is initialized
      (recursively) according to these rules

> >
> >>
> >>> +	};
> >>>
> >>>    	if (hex) {
> >>>    		if (get_sha1_hex(hex, sha1)){
> >>> @@ -81,9 +93,7 @@ void cgit_print_blob(const char *hex, char *path, const char *head)
> >>>
> >>>    	if((!hex) && type == OBJ_COMMIT && path) {
> >>>    		commit = lookup_commit_reference(sha1);
> >>> -		match_path = path;
> >>> -		matched_sha1 = sha1;
> >>> -		read_tree_recursive(commit->tree, "", 0, 0, paths, walk_tree, NULL);
> >>> +		read_tree_recursive(commit->tree, "", 0, 0, paths, walk_tree, &walk_tree_ctx);
> >>>    		type = sha1_object_info(sha1,&size);
> >>>    	}
> >>>
> >>>
> >>
> >> --
> >> Ferry Huberts
> 
> -- 
> Ferry Huberts
> 
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