[Bug]: UnsupportedSpecializationException with csv.reader

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#1,106 opened on Aug 25, 2026 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 3/5
Estimated time: 1-2 days
Newbie friendliness: 65/100

Issue type: Bug
Clarity: Mostly clear
Activity status: Active
Tech stack: java, python
Domain: compilers

Research direction

Start with the csv.CSVDialectBuiltins and CSVModuleBuiltins entry points named in the stack trace, then run the reported csv.reader(re.ASCII, int) reproducer. Trace how the unsupported argument is handled and add a regression test demonstrating that the call no longer crashes and produces the expected behavior.

Written by the indexing model from the issue text.

Description

bug

Describe the bug

GraalPy crashes when running this fuzzed code:

import re
from csv import reader
reader(re.ASCII, int)

Operating system

Linux

CPU architecture

x86_64

GraalPy version

GraalPy 3.13.14 (Oracle GraalVM Native 25.3.4.1)

JDK version

No response

Context configuration

No response

Steps to reproduce

Snippet listed above

Expected behavior

No crash

Stack trace

Unexpected values provided for CSVDialectBuiltinsFactory.DialectNodeFactory.DialectNodeGen@448c7dde: [Dialect, <class 'int'>, NoValue, NoValue, NoValue, NoValue, NoValue, NoValue, NoValue, NoValue], [PythonBuiltinClassType,PythonBuiltinClass,PNone,PNone,PNone,PNone,PNone,PNone,PNone,PNone]
com.oracle.truffle.api.dsl.UnsupportedSpecializationException: Unexpected values provided for CSVDialectBuiltinsFactory.DialectNodeFactory.DialectNodeGen@448c7dde: [Dialect, <class 'int'>, NoValue, NoValue, NoValue, NoValue, NoValue, NoValue, NoValue, NoValue], [PythonBuiltinClassType,PythonBuiltinClass,PNone,PNone,PNone,PNone,PNone,PNone,PNone,PNone]
	at org.graalvm.py/com.oracle.graal.python.builtins.modules.csv.CSVDialectBuiltinsFactory$DialectNodeFactory$DialectNodeGen.executeAndSpecialize(CSVDialectBuiltinsFactory.java:571)
	at org.graalvm.py/com.oracle.graal.python.builtins.modules.csv.CSVDialectBuiltinsFactory$DialectNodeFactory$DialectNodeGen.execute(CSVDialectBuiltinsFactory.java:434)
	at org.graalvm.py/com.oracle.graal.python.nodes.function.builtins.BuiltinCallNode$BuiltinAnyCallNode.execute(BuiltinCallNode.java:64)
	at org.graalvm.py/com.oracle.graal.python.nodes.function.BuiltinFunctionRootNode.execute(BuiltinFunctionRootNode.java:337)
	at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.executeRootNode(OptimizedCallTarget.java:808)
	at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.profiledPERoot(OptimizedCallTarget.java:722)
	at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callBoundary(OptimizedCallTarget.java:641)
	at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.invokeCallBoundary(SubstrateOptimizedCallTarget.java:124)
	at com.oracle.truffle.enterprise.svm/com.oracle.svm.enterprise.truffle.compiler.SubstrateEnterpriseOptimizedCallTarget.invokeCompiledAdapterOrCallBoundary(SubstrateEnterpriseOptimizedCallTarget.java:293)
	at com.oracle.truffle.enterprise.svm/com.oracle.svm.enterprise.truffle.compiler.SubstrateEnterpriseOptimizedCallTarget.invokeFromInterpreter(SubstrateEnterpriseOptimizedCallTarget.java:269)
	at com.oracle.truffle.enterprise.svm/com.oracle.svm.enterprise.truffle.compiler.SubstrateEnterpriseOptimizedCallTarget.doInvoke(SubstrateEnterpriseOptimizedCallTarget.java:255)
	at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callDirect(OptimizedCallTarget.java:573)
	at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedDirectCallNode.call(OptimizedDirectCallNode.java:94)
	at org.graalvm.py/com.oracle.graal.python.nodes.call.CallDispatchers$SimpleDirectInvokeNode.doDirect(CallDispatchers.java:128)
	at org.graalvm.py/com.oracle.graal.python.nodes.call.CallDispatchersFactory$SimpleDirectInvokeNodeGen$Inlined.executeAndSpecialize(CallDispatchersFactory.java:135)
	at org.graalvm.py/com.oracle.graal.python.nodes.call.CallDispatchersFactory$SimpleDirectInvokeNodeGen$Inlined.execute(CallDispatchersFactory.java:123)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargs$DispatchVarargsBuiltinFullDirectNode.call(TpSlotVarargs.java:282)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargsFactory$DispatchVarargsBuiltinFullDirectNodeGen$Inlined.executeAndSpecialize(TpSlotVarargsFactory.java:215)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargsFactory$DispatchVarargsBuiltinFullDirectNodeGen$Inlined.execute(TpSlotVarargsFactory.java:203)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargs$CallVarargsTpSlotBaseNode.callCachedBuiltin(TpSlotVarargs.java:254)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargsFactory$CallSlotTpNewNodeGen$Inlined.executeAndSpecialize(TpSlotVarargsFactory.java:1603)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargsFactory$CallSlotTpNewNodeGen$Inlined.execute(TpSlotVarargsFactory.java:1562)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.TypeBuiltins$CreateInstanceNode.doGeneric(TypeBuiltins.java:536)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.TypeBuiltinsFactory$CreateInstanceNodeGen$Inlined.executeAndSpecialize(TypeBuiltinsFactory.java:2021)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.TypeBuiltinsFactory$CreateInstanceNodeGen$Inlined.execute(TypeBuiltinsFactory.java:2009)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.TypeBuiltins$CallNode.call(TypeBuiltins.java:502)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.TypeBuiltinsFactory$CallNodeFactory$CallNodeGen.execute(TypeBuiltinsFactory.java:1820)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargs$CallVarargsTpSlotBaseNode.callCachedBuiltin(TpSlotVarargs.java:251)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargsFactory$CallSlotTpCallNodeGen$Inlined.executeAndSpecialize(TpSlotVarargsFactory.java:2220)
	at org.graalvm.py/com.oracle.graal.python.builtins.objects.type.slots.TpSlotVarargsFactory$CallSlotTpCallNodeGen$Inlined.execute(TpSlotVarargsFactory.java:2179)
	at org.graalvm.py/com.oracle.graal.python.nodes.call.CallNode.doGeneric(CallNode.java:217)
	at org.graalvm.py/com.oracle.graal.python.nodes.call.CallNodeGen.executeAndSpecialize(CallNodeGen.java:333)
	at org.graalvm.py/com.oracle.graal.python.nodes.call.CallNodeGen.executeInternal(CallNodeGen.java:249)
	at org.graalvm.py/com.oracle.graal.python.nodes.call.CallNode.execute(CallNode.java:128)
	at org.graalvm.py/com.oracle.graal.python.builtins.modules.csv.CSVModuleBuiltins$CSVReaderNode.createReader(CSVModuleBuiltins.java:241)
	at org.graalvm.py/com.oracle.graal.python.builtins.modules.csv.CSVModuleBuiltinsFactory$CSVReaderNodeFactory$CSVReaderNodeGen.executeAndSpecialize(CSVModuleBuiltinsFactory.java:907)
	at org.graalvm.py/com.oracle.graal.python.builtins.modules.csv.CSVModuleBuiltinsFactory$CSVReaderNodeFactory$CSVReaderNodeGen.execute(CSVModuleBuiltinsFactory.java:889)
	at org.graalvm.py/com.oracle.graal.python.nodes.function.builtins.BuiltinCallNode$BuiltinAnyCallNode.execute(BuiltinCallNode.java:64)
	at org.graalvm.py/com.oracle.graal.python.nodes.function.BuiltinFunctionRootNode.execute(BuiltinFunctionRootNode.java:337)
[...snip...]

Additional context

No response

Dominant language: Python
Stars: 1.6k
Forks: 155
Avg merge: 8h 20m
Merged PRs (30d): 43

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More Python issues

[Bug]: UnsupportedSpecializationException with csv.reader

Assessment

Research direction

Description

Describe the bug

Operating system

CPU architecture

GraalPy version

JDK version

Context configuration

Steps to reproduce

Expected behavior

Stack trace

Additional context

Contributor guide

First steps

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