shada: Only check errno if read/write returned -1

According to the manual (POSIX) this is the only case when errno is set by these
functions. This is needed because some functions (e.g. buflist_new) leave errno
set to non-zero value under some conditions (e.g. when opening non-existing
files).

1 files changed, 2 insertions, 2 deletions

diff --git a/src/nvim/shada.c b/src/nvim/shada.c
index da107ef38b..d7b3e27550 100644
--- a/src/nvim/shada.c
+++ b/src/nvim/shada.c
@@ -525,7 +525,7 @@ static ptrdiff_t read_file(ShaDaReadDef *const sd_reader, void *const dest,
       sd_reader->fpos += (uintmax_t) cur_read_bytes;
       assert(read_bytes <= size);
     }
-    if (errno) {
+    if (cur_read_bytes < 0) {
       if (errno == EINTR || errno == EAGAIN) {
         errno = 0;
         continue;
@@ -576,7 +576,7 @@ static ptrdiff_t write_file(ShaDaWriteDef *const sd_writer,
     if (cur_written_bytes > 0) {
       written_bytes += (size_t) cur_written_bytes;
     }
-    if (errno) {
+    if (cur_written_bytes < 0) {
       if (errno == EINTR || errno == EAGAIN) {
         errno = 0;
         continue;