test: check proper OP

brunoerg commented at 4:55 pm on July 23, 2025: contributor

According to corecheck, the following mutant is not caught by any test (https://corecheck.dev/mutation/src/script/interpreter.cpp).

 0diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
 1index 61ea7f4503..4f6fa34836 100644
 2--- a/src/script/interpreter.cpp
 3+++ b/src/script/interpreter.cpp
 4@@ -746,7 +746,6 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
 5                         return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 6                     valtype vch1 = stacktop(-6);
 7                     valtype vch2 = stacktop(-5);
 8-                    stack.erase(stack.end()-6, stack.end()-4);
 9                     stack.push_back(vch1);
10                     stack.push_back(vch2);
11                 }

It means we’re not testing the behavior of the OP_2ROT opcode properly. The normal behavior is: [1, 2, 3, 4, 5, 6] → OP_2ROT → [3, 4, 5, 6, 1, 2] (6 elements). However, by deleting the erase, it becomes: [1, 2, 3, 4, 5, 6] → OP_2ROT → [1, 2, 3, 4, 5, 6, 1, 2] (8 elements) which is obviously wrong. In script_tests.json, we have some test cases that includes the OP_2ROT which correctly tests the move part of 2ROT but not the erase one. See:

0["25 24 23 22 21 20", "2ROT 24 EQUAL", "P2SH,STRICTENC", "OK"],
1["25 24 23 22 21 20", "2ROT DROP 25 EQUAL", "P2SH,STRICTENC", "OK"],
2["25 24 23 22 21 20", "2ROT 2DROP 20 EQUAL", "P2SH,STRICTENC", "OK"],
3["25 24 23 22 21 20", "2ROT 2DROP DROP 21 EQUAL", "P2SH,STRICTENC", "OK"],
4["25 24 23 22 21 20", "2ROT 2DROP 2DROP 22 EQUAL", "P2SH,STRICTENC", "OK"],
5["25 24 23 22 21 20", "2ROT 2DROP 2DROP DROP 23 EQUAL", "P2SH,STRICTENC", "OK"],
6["25 24 23 22 21 20", "2ROT 2ROT 22 EQUAL", "P2SH,STRICTENC", "OK"],
7["25 24 23 22 21 20", "2ROT 2ROT 2ROT 20 EQUAL", "P2SH,STRICTENC", "OK"],

That said, this PR adds one more test case to the case mentioned.

test: check proper OP_2ROT behavior b94c6356a2

DrahtBot added the label Tests on Jul 23, 2025

DrahtBot commented at 4:55 pm on July 23, 2025: contributor

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/33047.

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ACK	l0rinc, w0xlt, maflcko

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l0rinc approved

l0rinc commented at 6:44 pm on July 23, 2025: contributor

ACK b94c6356a29b03def6337c91caabb3b8642187e8

I can confirm that the whole test suite passes when the stack erase is removed from the script interpreter code.

0rm -rf build && cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug && ninja -C build && build/bin/test_bitcoin --run_test=script_tests

 0diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
 1index 61ea7f4503..efb1af8137 100644
 2--- a/src/script/interpreter.cpp
 3+++ b/src/script/interpreter.cpp
 4@@ -746,7 +746,7 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
 5                         return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 6                     valtype vch1 = stacktop(-6);
 7                     valtype vch2 = stacktop(-5);
 8-                    stack.erase(stack.end()-6, stack.end()-4);
 9+                    // stack.erase(stack.end()-6, stack.end()-4);
10                     stack.push_back(vch1);
11                     stack.push_back(vch2);
12                 }
13diff --git a/src/test/data/script_tests.json b/src/test/data/script_tests.json
14index 6282f66649..c11bd68ae8 100644
15--- a/src/test/data/script_tests.json
16+++ b/src/test/data/script_tests.json
17@@ -105,7 +105,6 @@
18 ["25 24 23 22 21 20", "2ROT 2DROP 2DROP DROP 23 EQUAL", "P2SH,STRICTENC", "OK"],
19 ["25 24 23 22 21 20", "2ROT 2ROT 22 EQUAL", "P2SH,STRICTENC", "OK"],
20 ["25 24 23 22 21 20", "2ROT 2ROT 2ROT 20 EQUAL", "P2SH,STRICTENC", "OK"],
21-["1 2 3 4 5 6", "2ROT DEPTH 6 EQUAL", "P2SH,STRICTENC", "OK"],
22 ["1 0", "SWAP 1 EQUALVERIFY 0 EQUAL", "P2SH,STRICTENC", "OK"],
23 ["0 1", "TUCK DEPTH 3 EQUALVERIFY SWAP 2DROP", "P2SH,STRICTENC", "OK"],
24 ["13 14", "2DUP ROT EQUALVERIFY EQUAL", "P2SH,STRICTENC", "OK"],

And that it fails as expected with the new script_tests.json addition!

w0xlt commented at 1:42 am on July 24, 2025: contributor

ACK https://github.com/bitcoin/bitcoin/pull/33047/commits/b94c6356a29b03def6337c91caabb3b8642187e8

maflcko commented at 6:55 am on July 24, 2025: member

lgtm ACK b94c6356a29b03def6337c91caabb3b8642187e8

fanquake merged this on Jul 24, 2025

fanquake closed this on Jul 24, 2025

test: check proper OP_2ROT behavior #33047

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