Skip to content

compiler-detection.md

Latest commit

 

History

History
113 lines (89 loc) · 5.08 KB

compiler-detection.md

File metadata and controls

113 lines (89 loc) · 5.08 KB
Raw

Compiler detection — pinning the toolchain

Matching decomp lives or dies on using the same cl.exe and link.exe the original developers used. Getting this wrong by even a service pack can leave fundamental codegen mismatches (different __chkstk thresholds, different stack-protector cookie placement, different jump-table emission) that no amount of source tweaking will fix.

What the binary tells us

From IMAGE_OPTIONAL_HEADER:

MajorLinkerVersion = 8
MinorLinkerVersion = 0

Linker 8.0 ships with Visual Studio 2005. Microsoft's own mapping:

MSVC Visual Studio _MSC_VER cl.exe
7.0 VS 2002 1300 13.00.x
7.1 VS 2003 1310 13.10.x
8.0 VS 2005 1400 14.00.x
9.0 VS 2008 1500 15.00.x
10.0 VS 2010 1600 16.00.x
11.0 VS 2012 1700 17.00.x

So the toolchain is VS 2005, but VS 2005 had two service packs:

  • VS 2005 RTM — cl.exe 14.00.50727.42
  • VS 2005 SP1 — cl.exe 14.00.50727.762
  • VS 2005 SP1 + ATL Security Update — cl.exe 14.00.50727.4035

The release date of FFXIV ARR's predecessor, the original FFXIV 1.0 launch, is 2010-09-30 — the boot/updater builds are from 2010-09-16 which is two weeks before launch and well after VS 2005 SP1 (November 2006). The game was almost certainly built with VS 2005 SP1 (or SP1 + ATL update). RTM is unlikely — by 2010, no shipping title would still be on RTM.

We pick VS 2005 SP1 as the working hypothesis and verify on the Rosetta Stone function (see matching-workflow.md) by re-targeting SP1 vs RTM vs SP1+ATL and seeing which one matches default /O2 codegen for a 30-line landmark function. If SP1 fails and SP1+ATL matches, we switch.

Compiler flags hypothesis

Educated guesses for the original build flags, to seed flag-search:

Flag Why
/O2 Standard "favour speed" — every shipping game does this.
/Oy- or /Oy Frame-pointer omission. Ship games typically /Oy for speed.
/GR RTTI on (we observe RTTI in the binary).
/EHsc Standard SEH + C++ exceptions.
/Gy Function-level linking — necessary for /OPT:REF to be useful.
/GS- or /GS Buffer security check. Typically ON for retail; the binary's __security_cookie symbol will tell us which.
/Zc:wchar_t wchar_t as built-in. MSVC 2005 default is OFF; games often flip it on.
/Zc:forScope Standards-compliant for scoping.
/MT Static CRT linkage. Ship games avoid /MD (no DLL CRT dep).
/W3 or /W4 Compiler warnings — unobservable in binary.

We confirm each by inspection:

  • /MT vs /MD → look for MSVCR80.dll import. If absent, /MT.
  • /GS vs /GS- → grep .rdata for __security_cookie literal. If present and referenced from prologues, /GS is on.
  • /GR confirmed by RTTI presence (type_info, ??_R0 mangled symbols in .rdata).

tools/extract_pe.py (Phase 1) reports each of these.

Linker flags hypothesis

Flag Why
/SUBSYSTEM:WINDOWS Confirmed by header (subsystem=2).
/FIXED:NO Defaults; relocs_stripped characteristic is present so this is actually /FIXED — but games are typically loaded at 0x400000 regardless.
/STACK:reserve,commit Probe via IMAGE_OPTIONAL_HEADER.SizeOfStackReserve.
/HEAP:reserve,commit Same — read from header.
/SECTION:MSSMIXER,ER Custom section directive — Miles SDK shipped this.
/MERGE:.tls=.data (no) Their .tls is its own section.

The MSSMIXER section name is itself a fingerprint of the Miles Sound System SDK version that was shipped — RAD Game Tools' Miles 9.x of the era used MSSMIXER as the section name for the statically-linked mixer DSP. Knowing this avoids wasted effort "decompiling" what's actually third-party middleware; see known-libraries.md.

Confirmation procedure (Phase 2 deliverable)

# Procure VS 2005 SP1 and Platform SDK 2003 R2
./tools/setup-msvc.sh

# Pick a Rosetta Stone function. tools/find_rosetta.py scans the
# decompiler output for the smallest non-trivial function whose
# pseudo-C is unambiguous (e.g. a hand-rolled strncmp, an integer
# clamp helper). It writes src/ffxivgame/_rosetta/rosetta.cpp.

# Try compiling with each candidate toolchain.
for tc in vs2005-rtm vs2005-sp1 vs2005-sp1-atl; do
    make rosetta MSVC_TOOLCHAIN=$tc
    objdiff orig/ffxivgame.exe build/obj/_rosetta.obj
done

# Lock the winner into the Makefile.