Error running Ast::eliminate_conditions

[gibbed]

Thanks for your efforts on this project! It decompiles all but one script in my target without any visible errors so far.

Error running Ast::eliminate_conditions
Source: ast\ast.cpp:2367

Failed to eliminate all test and copy conditions

failing_script.zip

[marsinator358]

This is because of an edge case caused by a conditional assignment to a local that remains unused.
I already knew about this bug, but the fix is going to be part of a rewrite that won't happen for some time.

I've decompiled the file for you by manually fixing it with custom code, the error happens on line 100.
decompiled.zip

[gibbed]

Sounds good, thanks!

[marsinator358]

@Ezriral That would require quite a rework, it would be easier to just skip the entire current block.

But even that isn't necessary because once this gets fixed the decompiler
should be able to handle all unmodified luajit bytecode without any problems.

[marsinator358]

but there is still this nullptr error

That's because the repo is not up to date, please use the current executable instead.

I'm currently taking a break from this project (except bugfixes) so I won't implement anything right now, sorry.
If you have a file that fails to decompile you can send it to me though.

[gibbed]

That's because the repo is not up to date, please use the current executable instead.

If you could push your changes, that would be nice. No rush though.

My local changes are mostly for automation in my local setup that wouldn't make sense for the project in general.

I did figure out that the UTF8 detection for strings was bugged and fixed that in my local copy; which I assume is one of your non-pushed changes.

[marsinator358]

I did figure out that the UTF8 detection for strings was bugged

I didn't change anything since the original commit, could you please tell me what's wrong/show me an example?

[gibbed]

I didn't change anything since the original commit, could you please tell me what's wrong/show me an example?

Oh interesting. When I built luajit-decompiler-v2 locally, UTF8 strings were still getting escaped. I found char was getting sign extended, completely throwing off the building of the UTF value that's validated by your range checks.

My quick&dirty local fix:

diff --git a/lua/lua.cpp b/lua/lua.cpp
index e013f31..4ff5697 100644
--- a/lua/lua.cpp
+++ b/lua/lua.cpp
@@ -837,7 +837,7 @@ void Lua::write_string(const std::string& string) {
    uint8_t digit;

    for (uint32_t i = 0; i < string.size(); i++) {
-       value = string[i];
+       value = (uint8_t)string[i];

        if (!(value & 0x80)) {
            if (string[i] >= ' ' && string[i] <= '~') {
@@ -877,7 +877,7 @@ void Lua::write_string(const std::string& string) {
        } else if ((value & 0xE0) == 0xC0) {
            if (i <= string.size() - 2) {
                value <<= 8;
-               value |= string[i + 1];
+               value |= (uint8_t)string[i + 1];

                if ((value & 0xC0) == 0x80
                    && value >= 0xC280
@@ -891,8 +891,8 @@ void Lua::write_string(const std::string& string) {
        } else if ((value & 0xF0) == 0xE0) {
            if (i <= string.size() - 3) {
                value <<= 16;
-               value |= (uint16_t)string[i + 1] << 8;
-               value |= string[i + 2];
+               value |= (uint16_t)(uint8_t)string[i + 1] << 8;
+               value |= (uint8_t)string[i + 2];

                if ((value & 0xC0C0) == 0x8080
                    && ((value >= 0xE0A080
@@ -909,9 +909,9 @@ void Lua::write_string(const std::string& string) {
        } else if ((value & 0xF8) == 0xF0) {
            if (i <= string.size() - 4) {
                value <<= 24;
-               value |= (uint32_t)string[i + 1] << 16;
-               value |= (uint16_t)string[i + 2] << 8;
-               value |= string[i + 3];
+               value |= (uint32_t)(uint8_t)string[i + 1] << 16;
+               value |= (uint16_t)(uint8_t)string[i + 2] << 8;
+               value |= (uint8_t)string[i + 3];

                if ((value & 0xC0C0C0) == 0x808080
                    && value >= 0xF0908080

[marsinator358]

Oh that's because I'm using the /J option (default char is unsigned).

[Aussiemon]

@marsinator358 Here are 4 additional examples of "Error running Ast::eliminate_conditions at ast.cpp:2367", and 1 example with a different failure point and error message "Source: ast\ast.cpp:2271 (Failed to build condition in function 29)":

eliminate_conditions_compiled.zip eliminate_conditions_ljd_decompiled.zip

These files were tested with the latest binary in releases.

LuaJIT Decompiler v2
Compiled on Nov 21 2023
--------------------
Input file: \eliminate_conditions\bot_group.lua

Error running Ast::eliminate_conditions
Source: ast\ast.cpp:2367

Failed to eliminate all test and copy conditions
--------------------
Input file: \eliminate_conditions\item_stats_blueprints.lua

Error running Ast::eliminate_conditions
Source: ast\ast.cpp:2367

Failed to eliminate all test and copy conditions
--------------------
Input file: \eliminate_conditions\minion_attack.lua

Error running Ast::eliminate_conditions
Source: ast\ast.cpp:2367

Failed to eliminate all test and copy conditions
--------------------
Input file: \eliminate_conditions\qrencode.lua

Error running Ast::eliminate_conditions
Source: ast\ast.cpp:2271 (Failed to build condition in function 29)
--------------------
Input file: \eliminate_conditions\weapon_trait_templates.lua

Error running Ast::eliminate_conditions
Source: ast\ast.cpp:2367

Failed to eliminate all test and copy conditions
--------------------

[marsinator358]

@Aussiemon Thanks, only weapon_trait_templates.lua
has the same problem (ljd decompiled them as slot16 in the _test_template function). The others had different bugs.