X-Debbugs-CC: monnier@iro.umontreal.ca

* doc/lispref/processes.texi (Bindat Types): Expand the documentation
for the `str' and `strz' types to clarify expectations and explain
edge case behavior.
---
  doc/lispref/processes.texi | 26 +++++++++++++++++++++++---
  1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi
index 668a577870..68621d32a8 100644
--- a/doc/lispref/processes.texi
+++ b/doc/lispref/processes.texi
@@ -3479,11 +3479,31 @@ Bindat Types
  @var{bitlen} has to be a multiple of 8.
  
  @item str @var{len}
-String of bytes of length @var{len}.
+String of length @var{len}.  When packing, the first @var{len} bytes
+of the input string are copied to the packed output.  If the input
+string is shorter than @var{len}, the remaining bytes are set to zero.
+The input string must be unibyte (@pxref{Text Representations}).  When
+unpacking, any zero bytes in the packed input string will appear in
+the unpacked output.
  
  @item strz &optional @var{len}
-Zero-terminated string of bytes, can be of arbitrary length or in a fixed-size
-field with length @var{len}.
+If @var{len} is not provided: Variable-length null-terminated string.
+When packing, the entire input string is copied to the packed output
+followed by a zero byte (null terminator).  The input string must be
+unibyte (@pxref{Text Representations}) and must not contain any zero
+bytes.  When unpacking, the resulting string contains all bytes up to
+(but excluding) the null terminator.
+
+If @var{len} is provided: @code{strz} behaves the same as @code{str}
+with one difference. When unpacking, the first zero byte (null
+terminator) encountered in the packed string and all subsequent bytes
+are excluded from the unpacked result.
+
+@quotation Caution
+The packed output will not be null-terminated unless the input string
+is shorter than @var{len} or it contains a zero byte within the first
+@var{len} bytes.
+@end quotation
  
  @item vec @var{len} [@var{type}]
  Vector of @var{len} elements.  The type of the elements is given by
-- 
2.36.1