Retyping arrays silently fails

[rcaragea]

Testing idasql with an LLM workflow, I noticed that the models fail a couple times to retype an array, then switch to introducing a typedef due to a limitation in UPDATE ctree_lvars. It would be nice to have it working properly from the start.

Here's what I mean:

• In a function there is a variable detected as _DWORD v4[50];
• After supplying the following instructions: change v4 to a wchar_t array, it tries a few approaches which all fail with "cannot set lvar type: failed to parse type...":
  • UPDATE ctree_lvars SET type = 'wchar_t[100]' WHERE func_addr = 0x4014FA AND idx = 4
  • UPDATE ctree_lvars SET type = 'wchar_t v4[100]' WHERE func_addr = 0x4014FA AND idx = 4;
  • UPDATE ctree_lvars SET type = 'wchar_t[100]' WHERE func_addr = 0x4014FA AND idx = 4;
• I added a debug print after

  idasql/src/lib/src/decompiler.cpp

  Line 2212 in 8e552e5

  decl.sprnt("%s __x;", type_str);

  to the console plugin and, as inferred from the code, the problem is that the declarations aren't well formed:

Running parse_decl on: wchar_t[100] __x;
Running parse_decl on: wchar_t v4[100] __x;
Running parse_decl on: wchar_t[100] __x;

• Eventually it takes another approach and adds a typedef with:
  • SELECT parse_decls('typedef wchar_t wchar_array_100[100];');
  • UPDATE ctree_lvars SET type = 'wchar_array_100' WHERE func_addr = 0x4014FA AND idx = 4;

This approach works but it's kind of ugly to have to retry a couple times and add typedefs for each array size encountered.

I made a quick fix which seems to work but I'm unsure whether this is ideal:

diff --git a/src/lib/src/decompiler.cpp b/src/lib/src/decompiler.cpp
index c2073e2..f52f74f 100644
--- a/src/lib/src/decompiler.cpp
+++ b/src/lib/src/decompiler.cpp
@@ -2209,7 +2209,17 @@ bool set_lvar_type_at(ea_t func_addr, int lvar_idx, const char* type_str) {
     if (!tif.get_named_type(nullptr, type_str)) {
         // Use parse_decl for C declaration parsing
         qstring decl;
-        decl.sprnt("%s __x;", type_str);
+        if  (type_str && strchr(type_str, '[')) {
+            // Split the type string at the first '['
+            const char* bracket_pos = strchr(type_str, '[');
+            qstring base_type(type_str, bracket_pos - type_str);
+            qstring array_part(bracket_pos);  // includes the '[' and everything after
+            decl.sprnt("%s __x%s;", base_type.c_str(), array_part.c_str());
+        } else {
+                decl.sprnt("%s __x;", type_str);
+        }
+        // log the decl for debugging
+        msg("Running parse_decl on: %s\n", decl.c_str());
         qstring out_name;
         if (!parse_decl(&tif, &out_name, nullptr, decl.c_str(), PT_SIL)) {
             xsql::set_vtab_error(

Example input file attached test.zip

Thank you!

[0xeb]

Fixed for v0.0.18 (coming shortly). Array local-variable retyping works now (including scalarise→restore and multidimensional / pointer-to-array / named-type element cases). We handled it with a proper declarator parser (bracket-depth aware) rather than string-splitting, so the tricky forms parse correctly too. Thanks for the detailed repro, @rcaragea!