# [PATCH] cocci: detect useless free(3) calls 4 messages from 2017-02-11 to 2017-02-11. Participants: René Scharfe, Junio C Hamano, Lars Schneider. Thread: https://gitlist.dev/t/45113 ## René Scharfe, 2017-02-11 13:58 Subject: [PATCH] cocci: detect useless free(3) calls Message-ID: <7e10f934-f084-ceb4-00eb-b75cdb01886b@web.de> URL: https://gitlist.dev/e/7e10f934-f084-ceb4-00eb-b75cdb01886b%40web.de ``` Add a semantic patch for removing checks that cause free(3) to only be called with a NULL pointer, as that must be a programming mistake. Signed-off-by: Rene Scharfe --- No cases are found in master or next, but 1d263b93 (bisect--helper: `bisect_next_check` & bisect_voc shell function in C) introduced four of them to pu. contrib/coccinelle/free.cocci | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/contrib/coccinelle/free.cocci b/contrib/coccinelle/free.cocci index e28213161a..c03ba737e5 100644 --- a/contrib/coccinelle/free.cocci +++ b/contrib/coccinelle/free.cocci @@ -3,3 +3,9 @@ expression E; @@ - if (E) free(E); + +@@ +expression E; +@@ +- if (!E) + free(E); -- 2.11.1 ``` ## Junio C Hamano, 2017-02-11 19:01 Subject: Re: [PATCH] cocci: detect useless free(3) calls Message-ID: URL: https://gitlist.dev/e/xmqqr334h7rg.fsf%40gitster.mtv.corp.google.com In-Reply-To: <7e10f934-f084-ceb4-00eb-b75cdb01886b@web.de> ``` René Scharfe writes: > Add a semantic patch for removing checks that cause free(3) to only be > called with a NULL pointer, as that must be a programming mistake. > > Signed-off-by: Rene Scharfe > --- > No cases are found in master or next, but 1d263b93 (bisect--helper: > `bisect_next_check` & bisect_voc shell function in C) introduced four > of them to pu. Thanks. This should have been caught by code inspection, but having automated way to do so is always good. > > contrib/coccinelle/free.cocci | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/contrib/coccinelle/free.cocci b/contrib/coccinelle/free.cocci > index e28213161a..c03ba737e5 100644 > --- a/contrib/coccinelle/free.cocci > +++ b/contrib/coccinelle/free.cocci > @@ -3,3 +3,9 @@ expression E; > @@ > - if (E) > free(E); > + > +@@ > +expression E; > +@@ > +- if (!E) > + free(E); ``` ## Lars Schneider, 2017-02-11 19:31 Subject: Re: [PATCH] cocci: detect useless free(3) calls Message-ID: <5DF3AA3E-90C6-443C-A22C-489CE2C89A51@gmail.com> URL: https://gitlist.dev/e/5DF3AA3E-90C6-443C-A22C-489CE2C89A51%40gmail.com In-Reply-To: <7e10f934-f084-ceb4-00eb-b75cdb01886b@web.de> ``` > On 11 Feb 2017, at 14:58, René Scharfe wrote: > > Add a semantic patch for removing checks that cause free(3) to only be > called with a NULL pointer, as that must be a programming mistake. > > Signed-off-by: Rene Scharfe > --- > No cases are found in master or next, but 1d263b93 (bisect--helper: > `bisect_next_check` & bisect_voc shell function in C) introduced four > of them to pu. Hi Rene, how do you run these checks on the entire Git source? Do you run each semantic patch file on the source like this? spatch --sp-file contrib/coccinelle/qsort.cocci --dir /path/to/git/git ... spatch --sp-file contrib/coccinelle/free.cocci --dir /path/to/git/git How stable do you consider these checks? Would it make sense to run them as part of the Travis-CI build [1]? Thanks, Lars [1] https://travis-ci.org/git/git/branches ``` ## René Scharfe, 2017-02-11 19:50 Subject: Re: [PATCH] cocci: detect useless free(3) calls Message-ID: URL: https://gitlist.dev/e/ca01f8de-f5ce-2201-450d-cadd6aca7cb8%40web.de In-Reply-To: <5DF3AA3E-90C6-443C-A22C-489CE2C89A51@gmail.com> ``` Am 11.02.2017 um 20:31 schrieb Lars Schneider: > how do you run these checks on the entire Git source? > Do you run each semantic patch file on the source like this? > > spatch --sp-file contrib/coccinelle/qsort.cocci --dir /path/to/git/git > ... > spatch --sp-file contrib/coccinelle/free.cocci --dir /path/to/git/git With "make coccicheck", which runs spatch against the items in the make variable C_SOURCES, for all .cocci files. > How stable do you consider these checks? Would it make sense to run them > as part of the Travis-CI build [1]? There seem to have been problems with older versions[2], but I'm not aware of other issues. Having these checks run automatically would be nice because they require a special tool which I guess not everybody is willing (or able) to install and because they take multiple minutes. René [2] https://public-inbox.org/git/014ef44e-9dd8-40b3-a3ec-b483f938ee02@web.de/ ```