From 5fe27bcbfbce2edcab3d1663acb0ad23f45b5ea2 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Thu, 4 Apr 2019 16:54:04 +0200 Subject: [PATCH] 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 --- compat/mingw.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/compat/mingw.c b/compat/mingw.c index 3164814fc4..e4583ace62 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -2072,6 +2072,8 @@ 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) { free(w_key);