Intercept assert into runtime error.

.github/actions/compile-witness-generator/action.yml

@@ -83,6 +83,7 @@ runs:
         cp "${SOURCES_ROOT}/circom_adapter.hpp" "${CIRCUIT_CPP_PATH}/circom_adapter.hpp"
         cp "${SOURCES_ROOT}/circom_fwd.hpp" "${CIRCUIT_CPP_PATH}/circom_fwd.hpp"
         cp "${SOURCES_ROOT}/types.hpp" "${CIRCUIT_CPP_PATH}/types.hpp"
+        cp "${SOURCES_ROOT}/assert.h" "${CIRCUIT_CPP_PATH}/assert.h"
 
     # TODO: Instead of replace, make a fork that generates the appropriate Makefile
     - name: Replace ${{ inputs.circuit-name-display }}'s Makefile

justfile

@@ -35,7 +35,7 @@ poq: check-circom
     # circom-generated main() has no return on the success path; patch it before -O3 turns it into an infinite loop
     {{sed_i}} ':a;N;$!ba;s/\n}\n\n*$/\n  return 0;\n}/' blend/poq_cpp/main.cpp
     cp -r {{src}}/poq blend/poq_cpp/poq
-    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp blend/poq_cpp/
+    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp {{src}}/assert.h blend/poq_cpp/
     cp {{ci_makefile}} blend/poq_cpp/Makefile
     cp blend/test_ffi.cpp blend/poq_cpp/test_ffi.cpp
     make -C blend/poq_cpp PROJECT=poq linux-lib
@@ -51,7 +51,7 @@ pol: check-circom
     # circom-generated main() has no return on the success path; patch it before -O3 turns it into an infinite loop
     {{sed_i}} ':a;N;$!ba;s/\n}\n\n*$/\n  return 0;\n}/' mantle/pol_cpp/main.cpp
     cp -r {{src}}/pol mantle/pol_cpp/pol
-    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp mantle/pol_cpp/
+    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp {{src}}/assert.h mantle/pol_cpp/
     cp {{ci_makefile}} mantle/pol_cpp/Makefile
     cp mantle/test_pol.cpp mantle/pol_cpp/test_pol.cpp
     make -C mantle/pol_cpp PROJECT=pol linux-lib
@@ -67,7 +67,7 @@ poc: check-circom
     # circom-generated main() has no return on the success path; patch it before -O3 turns it into an infinite loop
     {{sed_i}} ':a;N;$!ba;s/\n}\n\n*$/\n  return 0;\n}/' mantle/poc_cpp/main.cpp
     cp -r {{src}}/poc mantle/poc_cpp/poc
-    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp mantle/poc_cpp/
+    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp {{src}}/assert.h mantle/poc_cpp/
     cp {{ci_makefile}} mantle/poc_cpp/Makefile
     cp mantle/test_poc.cpp mantle/poc_cpp/test_poc.cpp
     make -C mantle/poc_cpp PROJECT=poc linux-lib
@@ -83,7 +83,7 @@ signature: check-circom
     # circom-generated main() has no return on the success path; patch it before -O3 turns it into an infinite loop
     {{sed_i}} ':a;N;$!ba;s/\n}\n\n*$/\n  return 0;\n}/' mantle/signature_cpp/main.cpp
     cp -r {{src}}/signature mantle/signature_cpp/signature
-    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp mantle/signature_cpp/
+    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp {{src}}/assert.h mantle/signature_cpp/
     cp {{ci_makefile}} mantle/signature_cpp/Makefile
     cp mantle/test_signature.cpp mantle/signature_cpp/test_signature.cpp
     make -C mantle/signature_cpp PROJECT=signature linux-lib

src/assert.h

@@ -0,0 +1,25 @@
+// Assert-to-throw shim for circom-generated circuit code.
+//
+// Problem
+// -------
+// Circom generates C++ code that calls the standard assert() macro to enforce
+// circuit constraints (e.g. `assert(Fr_isTrue(&expaux[0]))`). When compiled
+// into a standalone binary, a failing assert aborts the subprocess and the
+// caller receives a non-zero exit code; an error. When compiled into a static
+// library and linked into the caller's process, the same abort kills the entire
+// process. A library must never call abort() on its caller.
+//
+// Mechanism
+// ---------
+// This file is copied into each circuit's build directory as assert.h. The
+// Makefile already passes -I. so the compiler finds this file before the
+// system assert.h when the generated code does `#include <assert.h>`.
+// #include_next <assert.h> pulls in the real system header (so all
+// declarations are present), then we redefine the assert macro to throw a
+// std::runtime_error instead of calling abort(). #pragma once prevents a
+// second include from re-running and undoing the redefinition.
+#pragma once
+#include_next <assert.h>
+#undef assert
+#include <stdexcept>
+#define assert(cond) ((cond) ? void(0) : throw std::runtime_error("Failed assert: " #cond))

src/poc/ffi.cpp

@@ -92,7 +92,13 @@ static Status generate_witness_impl(const WitnessInput* input, Bytes* output) {
     Circom_Circuit* circuit = loadCircuit(circuit_bytes);
     Circom_CalcWit* ctx = new Circom_CalcWit(circuit);
 
-    loadJson(ctx, input->inputs_json);
+    try {
+        loadJson(ctx, input->inputs_json);
+    } catch (...) {
+        delete ctx;
+        delete circuit;
+        throw;
+    }
     if (ctx->getRemaingInputsToBeSet()!=0) {
         const std::string message = "Not all inputs have been set. Only " + std::to_string(get_main_input_signal_no()-ctx->getRemaingInputsToBeSet()) + " out of " + std::to_string(get_main_input_signal_no()) + ".";
         delete ctx;

src/pol/ffi.cpp

@@ -92,7 +92,13 @@ static Status generate_witness_impl(const WitnessInput* input, Bytes* output) {
     Circom_Circuit* circuit = loadCircuit(circuit_bytes);
     Circom_CalcWit* ctx = new Circom_CalcWit(circuit);
 
-    loadJson(ctx, input->inputs_json);
+    try {
+        loadJson(ctx, input->inputs_json);
+    } catch (...) {
+        delete ctx;
+        delete circuit;
+        throw;
+    }
     if (ctx->getRemaingInputsToBeSet()!=0) {
         const std::string message = "Not all inputs have been set. Only " + std::to_string(get_main_input_signal_no()-ctx->getRemaingInputsToBeSet()) + " out of " + std::to_string(get_main_input_signal_no()) + ".";
         delete ctx;

src/poq/ffi.cpp

@@ -92,7 +92,13 @@ static Status generate_witness_impl(const WitnessInput* input, Bytes* output) {
     Circom_Circuit* circuit = loadCircuit(circuit_bytes);
     Circom_CalcWit* ctx = new Circom_CalcWit(circuit);
 
-    loadJson(ctx, input->inputs_json);
+    try {
+        loadJson(ctx, input->inputs_json);
+    } catch (...) {
+        delete ctx;
+        delete circuit;
+        throw;
+    }
     if (ctx->getRemaingInputsToBeSet()!=0) {
         const std::string message = "Not all inputs have been set. Only " + std::to_string(get_main_input_signal_no()-ctx->getRemaingInputsToBeSet()) + " out of " + std::to_string(get_main_input_signal_no()) + ".";
         delete ctx;

src/signature/ffi.cpp

@@ -92,7 +92,13 @@ static Status generate_witness_impl(const WitnessInput* input, Bytes* output) {
     Circom_Circuit* circuit = loadCircuit(circuit_bytes);
     Circom_CalcWit* ctx = new Circom_CalcWit(circuit);
 
-    loadJson(ctx, input->inputs_json);
+    try {
+        loadJson(ctx, input->inputs_json);
+    } catch (...) {
+        delete ctx;
+        delete circuit;
+        throw;
+    }
     if (ctx->getRemaingInputsToBeSet()!=0) {
         const std::string message = "Not all inputs have been set. Only " + std::to_string(get_main_input_signal_no()-ctx->getRemaingInputsToBeSet()) + " out of " + std::to_string(get_main_input_signal_no()) + ".";
         delete ctx;