wip: Build with -Wconversionlukeshu/safe-conversion

I think this found a real bug in the dhcp packet parser.

I don't think anything called lib9p_str{,n}() values that could be big
enough, but their bounds-checking was broken.

2 files changed, 5 insertions, 3 deletions

diff --git a/lib9p/core_gen/c_marshal.py b/lib9p/core_gen/c_marshal.py
index 322e1ef..581ed92 100644
--- a/lib9p/core_gen/c_marshal.py
+++ b/lib9p/core_gen/c_marshal.py
@@ -78,7 +78,7 @@ class OffsetExpr:
         if dsttyp:
             if not oneline:
                 oneline.append("0")
-            ret += f"{'\t'*indent_depth}{dsttyp} {dstvar} = {' + '.join(oneline)};\n"
+            ret += f"{'\t'*indent_depth}{dsttyp} {dstvar} = LM_SAFEDOWNCAST({dsttyp}, {' + '.join(oneline)});\n"
         elif oneline:
             ret += f"{'\t'*indent_depth}{dstvar} += {' + '.join(oneline)};\n"
         ret += multiline
@@ -350,6 +350,8 @@ def gen_c_marshal(versions: set[str], typs: list[idl.UserType]) -> str:
                     return f"offsetof{''.join('_'+m.membname for m in path.elems[:-1])}_{sym}"
 
                 val = c9util.idl_expr(child.val, lookup_sym)
+                if child.typ.static_size < 32:
+                    val = f"LM_SAFEDOWNCAST(uint{child.typ.static_size*8}_t, {val})"
             else:
                 val = path.c_str("val->")
             if isinstance(child.typ, idl.Bitfield):
diff --git a/lib9p/core_gen/h.py b/lib9p/core_gen/h.py
index 61775c1..378fc06 100644
--- a/lib9p/core_gen/h.py
+++ b/lib9p/core_gen/h.py
@@ -354,14 +354,14 @@ enum {c9util.ident('version')} {{
 
     ret += "\n"
     ret += f"struct {c9util.ident('Tmsg_send_buf')} {{\n"
-    ret += "\tsize_t          iov_cnt;\n"
+    ret += "\tint             iov_cnt;\n"
     ret += f"\tstruct iovec    iov[{c9util.IDENT('TMSG_MAX_IOV')}];\n"
     ret += f"\tuint8_t         copied[{c9util.IDENT('TMSG_MAX_COPY')}];\n"
     ret += "};\n"
 
     ret += "\n"
     ret += f"struct {c9util.ident('Rmsg_send_buf')} {{\n"
-    ret += "\tsize_t          iov_cnt;\n"
+    ret += "\tint             iov_cnt;\n"
     ret += f"\tstruct iovec    iov[{c9util.IDENT('RMSG_MAX_IOV')}];\n"
     ret += f"\tuint8_t         copied[{c9util.IDENT('RMSG_MAX_COPY')}];\n"
     ret += "};\n"