cutils: Set value in all integral qemu_strto* error paths

Our goal in writing qemu_strtoi() and friends is to have an interface
harder to abuse than libc's strtol().  Leaving the return value
uninitialized on some but not all error paths does not lend itself
well to this goal; and our documentation wasn't helpful on what to
expect.

Note that the previous patch changed all qemu_strtosz() EINVAL error
paths to slam value to 0 rather than stay uninitialized, even when the
EINVAL eror occurs because of trailing junk.  But for the remaining
integral qemu_strto*, it's easier to return the parsed value than to
force things back to zero, in part because of how check_strtox_error
works; in part because people expect that from libc strto* (while
there is no libc strtosz to compare to), and in part because doing so
creates less churn in the testsuite.

Here, the list of affected callers is much longer ('git grep
"qemu_strto[ui]" "*.c" "**/*.c" | grep -v tests/ |wc -l' outputs 107,
although a few of those are the implementation in in cutils.c), so
touching as little as possible is the wisest course of action.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20230522190441.64278-17-eblake@redhat.com>

1 files changed, 26 insertions, 16 deletions

diff --git a/util/cutils.c b/util/cutils.c
index c5530a5c2b..edfb71a217 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -384,12 +384,13 @@ static int check_strtox_error(const char *nptr, char *ep,
  *
  * @nptr may be null, and no conversion is performed then.
  *
- * If no conversion is performed, store @nptr in *@endptr and return
- * -EINVAL.
+ * If no conversion is performed, store @nptr in *@endptr, 0 in
+ * @result, and return -EINVAL.
  *
  * If @endptr is null, and the string isn't fully converted, return
- * -EINVAL.  This is the case when the pointer that would be stored in
- * a non-null @endptr points to a character other than '\0'.
+ * -EINVAL with @result set to the parsed value.  This is the case
+ * when the pointer that would be stored in a non-null @endptr points
+ * to a character other than '\0'.
  *
  * If the conversion overflows @result, store INT_MAX in @result,
  * and return -ERANGE.
@@ -410,6 +411,7 @@ int qemu_strtoi(const char *nptr, const char **endptr, int base,
 
     assert((unsigned) base <= 36 && base != 1);
     if (!nptr) {
+        *result = 0;
         if (endptr) {
             *endptr = nptr;
         }
@@ -439,12 +441,13 @@ int qemu_strtoi(const char *nptr, const char **endptr, int base,
  *
  * @nptr may be null, and no conversion is performed then.
  *
- * If no conversion is performed, store @nptr in *@endptr and return
- * -EINVAL.
+ * If no conversion is performed, store @nptr in *@endptr, 0 in
+ * @result, and return -EINVAL.
  *
  * If @endptr is null, and the string isn't fully converted, return
- * -EINVAL.  This is the case when the pointer that would be stored in
- * a non-null @endptr points to a character other than '\0'.
+ * -EINVAL with @result set to the parsed value.  This is the case
+ * when the pointer that would be stored in a non-null @endptr points
+ * to a character other than '\0'.
  *
  * If the conversion overflows @result, store UINT_MAX in @result,
  * and return -ERANGE.
@@ -465,6 +468,7 @@ int qemu_strtoui(const char *nptr, const char **endptr, int base,
 
     assert((unsigned) base <= 36 && base != 1);
     if (!nptr) {
+        *result = 0;
         if (endptr) {
             *endptr = nptr;
         }
@@ -508,12 +512,13 @@ int qemu_strtoui(const char *nptr, const char **endptr, int base,
  *
  * @nptr may be null, and no conversion is performed then.
  *
- * If no conversion is performed, store @nptr in *@endptr and return
- * -EINVAL.
+ * If no conversion is performed, store @nptr in *@endptr, 0 in
+ * @result, and return -EINVAL.
  *
  * If @endptr is null, and the string isn't fully converted, return
- * -EINVAL.  This is the case when the pointer that would be stored in
- * a non-null @endptr points to a character other than '\0'.
+ * -EINVAL with @result set to the parsed value.  This is the case
+ * when the pointer that would be stored in a non-null @endptr points
+ * to a character other than '\0'.
  *
  * If the conversion overflows @result, store LONG_MAX in @result,
  * and return -ERANGE.
@@ -530,6 +535,7 @@ int qemu_strtol(const char *nptr, const char **endptr, int base,
 
     assert((unsigned) base <= 36 && base != 1);
     if (!nptr) {
+        *result = 0;
         if (endptr) {
             *endptr = nptr;
         }
@@ -550,12 +556,13 @@ int qemu_strtol(const char *nptr, const char **endptr, int base,
  *
  * @nptr may be null, and no conversion is performed then.
  *
- * If no conversion is performed, store @nptr in *@endptr and return
- * -EINVAL.
+ * If no conversion is performed, store @nptr in *@endptr, 0 in
+ * @result, and return -EINVAL.
  *
  * If @endptr is null, and the string isn't fully converted, return
- * -EINVAL.  This is the case when the pointer that would be stored in
- * a non-null @endptr points to a character other than '\0'.
+ * -EINVAL with @result set to the parsed value.  This is the case
+ * when the pointer that would be stored in a non-null @endptr points
+ * to a character other than '\0'.
  *
  * If the conversion overflows @result, store ULONG_MAX in @result,
  * and return -ERANGE.
@@ -573,6 +580,7 @@ int qemu_strtoul(const char *nptr, const char **endptr, int base,
 
     assert((unsigned) base <= 36 && base != 1);
     if (!nptr) {
+        *result = 0;
         if (endptr) {
             *endptr = nptr;
         }
@@ -601,6 +609,7 @@ int qemu_strtoi64(const char *nptr, const char **endptr, int base,
 
     assert((unsigned) base <= 36 && base != 1);
     if (!nptr) {
+        *result = 0;
         if (endptr) {
             *endptr = nptr;
         }
@@ -628,6 +637,7 @@ int qemu_strtou64(const char *nptr, const char **endptr, int base,
 
     assert((unsigned) base <= 36 && base != 1);
     if (!nptr) {
+        *result = 0;
         if (endptr) {
             *endptr = nptr;
         }