path: root/compat/mingw.c
diff options
authorJohannes Schindelin <>2019-10-04 15:09:30 (GMT)
committerJunio C Hamano <>2019-10-06 00:07:44 (GMT)
commit61d1d92aa4785090213e89566e01e342f60d9b92 (patch)
tree2dd361dbad18bf32b0351388f20e056224836a22 /compat/mingw.c
parente4347c943416da5aef56ee70c4488bc0725dfd2a (diff)
msvc: work around a bug in GetEnvironmentVariable()
The return value of that function is 0 both for variables that are unset, as well as for variables whose values are empty. To discern those two cases, one has to call `GetLastError()`, whose return value is `ERROR_ENVVAR_NOT_FOUND` and `ERROR_SUCCESS`, respectively. Except that it is not actually set to `ERROR_SUCCESS` in the latter case, apparently, but the last error value seems to be simply unchanged. To work around this, let's just re-set the last error value just before inspecting the environment variable. This fixes a problem that triggers failures in (where we try to override config settings by passing empty values for certain environment variables). This problem is hidden in the MINGW build by the fact that older MSVC runtimes (such as the one used by MINGW builds) have a `calloc()` that re-sets the last error value in case of success, while newer runtimes set the error value only if `NULL` is returned by that function. Signed-off-by: Johannes Schindelin <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'compat/mingw.c')
1 files changed, 2 insertions, 0 deletions
diff --git a/compat/mingw.c b/compat/mingw.c
index 4891789..7d8cb81 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1661,6 +1661,8 @@ char *mingw_getenv(const char *name)
if (!w_key)
die("Out of memory, (tried to allocate %u wchar_t's)", len_key);
xutftowcs(w_key, name, len_key);
+ /* GetEnvironmentVariableW() only sets the last error upon failure */
+ SetLastError(ERROR_SUCCESS);
len_value = GetEnvironmentVariableW(w_key, w_value, ARRAY_SIZE(w_value));
if (!len_value && GetLastError() == ERROR_ENVVAR_NOT_FOUND) {