@matheusbsbs / matheus-bagliano / commits / 61d1d92aa4

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 t3301-notes.sh (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 <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Johannes Schindelin committed Oct 4, 2019 at 08:09 UTC 61d1d92aa4785090213e89566e01e342f60d9b92

1 file changed +2

compat/mingw.c

@@ -1661,6 +1661,8 @@ char *mingw_getenv(const char *name)

1661 if (!w_key)

1662 die("Out of memory, (tried to allocate %u wchar_t's)", len_key);

1663 xutftowcs(w_key, name, len_key);

1664 + /* GetEnvironmentVariableW() only sets the last error upon failure */

1665 + SetLastError(ERROR_SUCCESS);

1666 len_value = GetEnvironmentVariableW(w_key, w_value, ARRAY_SIZE(w_value));

1667 if (!len_value && GetLastError() == ERROR_ENVVAR_NOT_FOUND) {

1668 free(w_key);