SLANG_DISABLE_EXCEPTIONS does not compile

[pdeayton-nv]

Issue Description

Slang does not compile when SLANG_DISABLE_EXCEPTIONS is defined and C++ exceptions are disabled.

Reproducer Code

From a checkout with submodules initialized:

g++ -std=c++20 -fno-exceptions -DSLANG_DISABLE_EXCEPTIONS=1 \
  -Iinclude -Isource -Iexternal/unordered_dense/include \
  -c source/core/slang-token-reader.cpp

Expected Behavior

Slang compiles successfully when SLANG_DISABLE_EXCEPTIONS is defined and the toolchain has C++ exception support disabled.

Actual Behavior

source/core/slang-token-reader.h:176:70: error: exception handling disabled, use ‘-fexceptions’ to enable

Environment

• Slang: v2026.16-31-gc1cffad25

[nv-slang-bot]

Triage — reproduced ✅

• Status: Reproduced on top-of-tree (HEAD c1cffad25, matches reported v2026.16-31-gc1cffad25). The exact command fails at source/core/slang-token-reader.h:176:70 with error: exception handling disabled. Not a regression — these throws predate the only recent touch to the file.
• Root cause: source/core/slang-token-reader.h has 10 bare throw TextFormatException(...) sites (lines 176, 185, 203, 213, 222, 231, 240, 250, 258, 270) inside inline TokenReader methods. These are the only unguarded throws in source/core (no try/catch blocks exist there). The codebase's design intent (slang-exception.h:9-14, slang.h:313) is that core/compiler-core compile cleanly with exceptions disabled by routing through the signal mechanism instead — as slang-signal.cpp:164-182 already does with #if SLANG_HAS_EXCEPTIONS.
• Classification: bug / medium / P2 / component: core (build-config & portability). Issue Type set to Bug, reproduced applied.
• Recommended fix: Add one inline [[noreturn]] raiseTextFormatException(String) helper guarded by #if SLANG_HAS_EXCEPTIONS (throws when enabled — preserving the genuine catch at slang-ir-spirv-snippet.cpp:318 — else SLANG_UNEXPECTED(...)), and replace the 10 throws with it. A patched copy compiles cleanly both with -fno-exceptions -DSLANG_DISABLE_EXCEPTIONS=1 and with exceptions enabled (validated locally). One error-raising choke point, mirrors the existing handleSignal pattern.
• Next-action: Handed to the fixer with a full briefing (approaches, tradeoffs, proven build check). Fix incoming via a draft PR. Consider a CI variant that compiles core/compiler-core with exceptions disabled to prevent recurrence (no such build option exists today).

_{🤖 Generated by an automated Slang coworker — may be inaccurate. A human maintainer should verify.}

[nv-slang-bot]

Fix drafted — PR #12782

• Status: Fixed; draft PR Fix #12779: compile core with SLANG_DISABLE_EXCEPTIONS #12782 open against master (CI triggered).
• Root cause: The 10 bare throw TextFormatException(...) in the inline TokenReader methods of source/core/slang-token-reader.h — the only unguarded throws in source/core — fail to compile under -fno-exceptions -DSLANG_DISABLE_EXCEPTIONS=1.
• Fix: Route all 10 through one [[noreturn]] inline raiseTextFormatException(String) helper guarded by #if SLANG_HAS_EXCEPTIONS — throws when exceptions are enabled (preserving the recovery catch in slang-ir-spirv-snippet.cpp and the render-test/unit-test catches), else SLANG_UNEXPECTED(...). Mirrors handleSignal in slang-signal.cpp.
• Verified: your exact reproducer now compiles; -fexceptions and -fno-exceptions -DSLANG_DISABLE_EXCEPTIONS=1 -Werror=return-type also compile; full debug build links; 16/16 tokenReader unit tests pass (including the throw-path tests).
• Next-action: One open question for the maintainer in the PR — a runtime test can't catch a build-config compile break, so I've left a proposed CI leg that compiles core with exceptions disabled as an explicit maintainer decision rather than bundling a workflow change into this one-file fix.

_{🤖 Generated by an automated Slang coworker — may be inaccurate. A human maintainer should verify.}