| Message ID | 20190111202608.10576-1-kgybels@infogroep.be (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] diff: ensure correct lifetime of external_diff_cmd | expand |
Kim Gybels <kgybels@infogroep.be> writes: > According to getenv(3)'s notes: > > The implementation of getenv() is not required to be reentrant. The > string pointed to by the return value of getenv() may be statically > allocated, and can be modified by a subsequent call to getenv(), > putenv(3), setenv(3), or unsetenv(3). > ... > Signed-off-by: Kim Gybels <kgybels@infogroep.be> > --- Thanks, looking good. Will queue. > > Uses xstrdup_or_null as suggested by Eric Sunshine. > > diff.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/diff.c b/diff.c > index dc9965e836..5634992bbc 100644 > --- a/diff.c > +++ b/diff.c > @@ -487,11 +487,11 @@ static const char *external_diff(void) > static const char *external_diff_cmd = NULL; > static int done_preparing = 0; > > if (done_preparing) > return external_diff_cmd; > - external_diff_cmd = getenv("GIT_EXTERNAL_DIFF"); > + external_diff_cmd = xstrdup_or_null(getenv("GIT_EXTERNAL_DIFF")); > if (!external_diff_cmd) > external_diff_cmd = external_diff_cmd_cfg; > done_preparing = 1; > return external_diff_cmd; > }
diff --git a/diff.c b/diff.c index dc9965e836..5634992bbc 100644 --- a/diff.c +++ b/diff.c @@ -487,11 +487,11 @@ static const char *external_diff(void) static const char *external_diff_cmd = NULL; static int done_preparing = 0; if (done_preparing) return external_diff_cmd; - external_diff_cmd = getenv("GIT_EXTERNAL_DIFF"); + external_diff_cmd = xstrdup_or_null(getenv("GIT_EXTERNAL_DIFF")); if (!external_diff_cmd) external_diff_cmd = external_diff_cmd_cfg; done_preparing = 1; return external_diff_cmd; }
According to getenv(3)'s notes: The implementation of getenv() is not required to be reentrant. The string pointed to by the return value of getenv() may be statically allocated, and can be modified by a subsequent call to getenv(), putenv(3), setenv(3), or unsetenv(3). Since strings returned by getenv() are allowed to change on subsequent calls to getenv(), make sure to duplicate when caching external_diff_cmd from environment. This problem becomes apparent on Git for Windows since fe21c6b285df (mingw: reencode environment variables on the fly (UTF-16 <-> UTF-8)), when the getenv() implementation provided in compat/mingw.c was changed to keep a certain amount of alloc'ed strings and freeing them on subsequent calls. This fixes https://github.com/git-for-windows/git/issues/2007: $ yes n | git -c difftool.prompt=yes difftool fe21c6b285df fe21c6b285df~100 Viewing (1/404): '.gitignore' Launch 'bc3' [Y/n]? Viewing (2/404): 'Documentation/.gitignore' Launch 'bc3' [Y/n]? Viewing (3/404): 'Documentation/Makefile' Launch 'bc3' [Y/n]? Viewing (4/404): 'Documentation/RelNotes/2.14.5.txt' Launch 'bc3' [Y/n]? Viewing (5/404): 'Documentation/RelNotes/2.15.3.txt' Launch 'bc3' [Y/n]? Viewing (6/404): 'Documentation/RelNotes/2.16.5.txt' Launch 'bc3' [Y/n]? Viewing (7/404): 'Documentation/RelNotes/2.17.2.txt' Launch 'bc3' [Y/n]? Viewing (8/404): 'Documentation/RelNotes/2.18.1.txt' Launch 'bc3' [Y/n]? Viewing (9/404): 'Documentation/RelNotes/2.19.0.txt' Launch 'bc3' [Y/n]? error: cannot spawn ¦?: No such file or directory fatal: external diff died, stopping at Documentation/RelNotes/2.19.1.txt Signed-off-by: Kim Gybels <kgybels@infogroep.be> --- Uses xstrdup_or_null as suggested by Eric Sunshine. diff.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)