# [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix() 5 messages from 2014-03-18 to 2014-03-19. Participants: Othman Darraz, Eric Sunshine, Michael Haggerty. Thread: https://gitlist.dev/t/36211 ## Othman Darraz, 2014-03-18 22:41 Subject: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix() Message-ID: <1395182512-17179-1-git-send-email-darrazo16@gmail.com> URL: https://gitlist.dev/e/1395182512-17179-1-git-send-email-darrazo16%40gmail.com ``` use of starts_with() instead of memcmp() use of skip_prefix instead of memcmp() and strlen() Signed-off-by: Othman Darraz --- I am planning to apply to GSOC 214 fsck.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fsck.c b/fsck.c index 64bf279..5eae856 100644 --- a/fsck.c +++ b/fsck.c @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func) int parents = 0; int err; - if (memcmp(buffer, "tree ", 5)) + if (starts_with(buffer, "tree ")) return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line"); if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n') return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1"); @@ -322,15 +322,15 @@ static int fsck_commit(struct commit *commit, fsck_error error_func) if (p || parents) return error_func(&commit->object, FSCK_ERROR, "parent objects missing"); } - if (memcmp(buffer, "author ", 7)) + if (starts_with(buffer, "author ")) return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line"); buffer += 7; err = fsck_ident(&buffer, &commit->object, error_func); if (err) return err; - if (memcmp(buffer, "committer ", strlen("committer "))) + buffer = (char* )skip_prefix(buffer,"committer "); + if (!buffer) return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line"); - buffer += strlen("committer "); err = fsck_ident(&buffer, &commit->object, error_func); if (err) return err; -- 1.9.0.258.g00eda23.dirty ``` ## Eric Sunshine, 2014-03-18 23:09 Subject: Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix() Message-ID: URL: https://gitlist.dev/e/CAPig%2BcRoRzZKjW3cY86iQxz9iZ_TKT-yyu%3D6Va5aV_DsCAQquA%40mail.gmail.com In-Reply-To: <1395182512-17179-1-git-send-email-darrazo16@gmail.com> ``` Thanks for the submission. Comments below to give you a taste of the Git review process... On Tue, Mar 18, 2014 at 6:41 PM, Othman Darraz wrote: > use of starts_with() instead of memcmp() > > use of skip_prefix instead of memcmp() and strlen() Write proper sentences to explain and justify the change; not sentence fragments. > Signed-off-by: Othman Darraz > --- > > I am planning to apply to GSOC 214 Your logic in these changes is rather severely flawed. Running the test suite (t1450, in particular), as the GSoC microproject page suggests, would have clued you in that something was amiss. > fsck.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/fsck.c b/fsck.c > index 64bf279..5eae856 100644 > --- a/fsck.c > +++ b/fsck.c > @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func) > int parents = 0; > int err; > > - if (memcmp(buffer, "tree ", 5)) > + if (starts_with(buffer, "tree ")) > return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line"); > if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n') One of the reasons for using starts_with() rather than memcmp() is that it allows you to eliminate magic numbers, such as 5. However, if you look closely at this code fragment, you will see that the magic number is still present in the expression 'buffer+5'. starts_with(), might be a better fit. > return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1"); > @@ -322,15 +322,15 @@ static int fsck_commit(struct commit *commit, fsck_error error_func) > if (p || parents) > return error_func(&commit->object, FSCK_ERROR, "parent objects missing"); > } > - if (memcmp(buffer, "author ", 7)) > + if (starts_with(buffer, "author ")) > return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line"); > buffer += 7; Same problem here with magic number 7. > err = fsck_ident(&buffer, &commit->object, error_func); > if (err) > return err; > - if (memcmp(buffer, "committer ", strlen("committer "))) > + buffer = (char* )skip_prefix(buffer,"committer "); Style: (char *) Style: whitespace: skip_prefix(foo, "bar") Regarding the (char *) cast: Is 'buffer' ever modified in this function? If not, would it make sense to make it 'const' (and fix any other small fallout from that change)? > + if (!buffer) > return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line"); > - buffer += strlen("committer "); > err = fsck_ident(&buffer, &commit->object, error_func); > if (err) > return err; > -- > 1.9.0.258.g00eda23.dirty ``` ## Eric Sunshine, 2014-03-18 23:12 Subject: Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix() Message-ID: URL: https://gitlist.dev/e/CAPig%2BcQko2fdCVmNyTufpGW%3DRRCxVt5G4xdWC7OrQmC9nXfKzg%40mail.gmail.com In-Reply-To: ``` On Tue, Mar 18, 2014 at 7:09 PM, Eric Sunshine wrote: >> diff --git a/fsck.c b/fsck.c >> index 64bf279..5eae856 100644 >> --- a/fsck.c >> +++ b/fsck.c >> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func) >> int parents = 0; >> int err; >> >> - if (memcmp(buffer, "tree ", 5)) >> + if (starts_with(buffer, "tree ")) >> return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line"); >> if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n') > > One of the reasons for using starts_with() rather than memcmp() is > that it allows you to eliminate magic numbers, such as 5. However, if > you look closely at this code fragment, you will see that the magic > number is still present in the expression 'buffer+5'. starts_with(), > might be a better fit. Of course, I meant "skip_prefix() might be a better fit". ``` ## Michael Haggerty, 2014-03-18 23:16 Subject: Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix() Message-ID: <5328D3C0.5080009@alum.mit.edu> URL: https://gitlist.dev/e/5328D3C0.5080009%40alum.mit.edu In-Reply-To: ``` On 03/19/2014 12:09 AM, Eric Sunshine wrote: > Thanks for the submission. Comments below to give you a taste of the > Git review process... > > On Tue, Mar 18, 2014 at 6:41 PM, Othman Darraz wrote: >> use of starts_with() instead of memcmp() >> >> use of skip_prefix instead of memcmp() and strlen() > > Write proper sentences to explain and justify the change; not sentence > fragments. > >> Signed-off-by: Othman Darraz >> --- >> >> I am planning to apply to GSOC 214 > > Your logic in these changes is rather severely flawed. Running the > test suite (t1450, in particular), as the GSoC microproject page > suggests, would have clued you in that something was amiss. > >> fsck.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/fsck.c b/fsck.c >> index 64bf279..5eae856 100644 >> --- a/fsck.c >> +++ b/fsck.c >> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func) >> int parents = 0; >> int err; >> >> - if (memcmp(buffer, "tree ", 5)) >> + if (starts_with(buffer, "tree ")) >> return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line"); >> if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n') > > One of the reasons for using starts_with() rather than memcmp() is > that it allows you to eliminate magic numbers, such as 5. However, if > you look closely at this code fragment, you will see that the magic > number is still present in the expression 'buffer+5'. starts_with(), > might be a better fit. Eric, I think you meant to say that *skip_prefix()* might be a better fit. > [...] Michael -- Michael Haggerty mhagger@alum.mit.edu http://softwareswirl.blogspot.com/ ``` ## Eric Sunshine, 2014-03-19 09:33 Subject: Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix() Message-ID: URL: https://gitlist.dev/e/CAPig%2BcQ%3D3tjC47FgPRFkDW1dgE9p1uKsAiZ6uZoNXR0mBMjuBA%40mail.gmail.com In-Reply-To: ``` On Wed, Mar 19, 2014 at 5:04 AM, Othman Darraz wrote: > 2014-03-19 0:12 GMT+01:00 Eric Sunshine : >> On Tue, Mar 18, 2014 at 7:09 PM, Eric Sunshine >> wrote: >> >> >> diff --git a/fsck.c b/fsck.c >> >> index 64bf279..5eae856 100644 >> >> --- a/fsck.c >> >> +++ b/fsck.c >> >> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, >> >> fsck_error error_func) >> >> int parents = 0; >> >> int err; >> >> >> >> - if (memcmp(buffer, "tree ", 5)) >> >> + if (starts_with(buffer, "tree ")) >> >> return error_func(&commit->object, FSCK_ERROR, "invalid >> >> format - expected 'tree' line"); >> >> if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n') >> > >> > One of the reasons for using starts_with() rather than memcmp() is >> > that it allows you to eliminate magic numbers, such as 5. However, if >> > you look closely at this code fragment, you will see that the magic >> > number is still present in the expression 'buffer+5'. starts_with(), >> > might be a better fit. >> >> Of course, I meant "skip_prefix() might be a better fit". > > Thank you for your review and feedbacks. > Actually I made a mistake because I misunderstood how to run the tests, I > was using the wrong Makefile. For quick initial testing, you can just run the single test script. For instance: (cd t && ./t1450-fsck.sh) Once you have that running correctly, then run the entire test suite to ensure that your changes didn't break anything else. > Secondly I think , as well, that skip_prefix() > is a better fit. Nevertheless, as the variable buffer change in this > function, using skip_prefix() implies the use of cast. Yes, the variable named 'buffer' changes, but does the content of the memory referenced by 'buffer' ever change? If not, then 'buffer' could be made 'const', thus eliminating the need for the cast. (Note that changing it to 'const' might involve a bit of extra work, but the question is still pertinent.) > I will make the > changes right now. > > Thank you for your time. > > Othman DARRAZ ```