C: Fix negative string index #1138
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Smit-create
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certik
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Sep 23, 2022
integration_tests/test_str_03.py
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| # runtime tests | ||
| k: i32 = len(a); i: i32 | ||
| for i in range(k): | ||
| assert a[-i-1] == a[k-i-1] |
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For the same reason as discussed in the PR for negative list indices, we should not allow runtime negative string indices, because they can't be implemented in LLVM/C with high performance (that is, without an extra check for every index access).
We can however allow compile time negative value, because there is no runtime penalty.
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Oh okay, get it. I'll revert the last two commits.
certik
reviewed
Sep 23, 2022
src/libasr/codegen/asr_to_c.cpp
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| @@ -806,8 +806,9 @@ R"( | |||
| std::string idx = std::move(src); | |||
| this->visit_expr(*x.m_arg); | |||
| std::string str = std::move(src); | |||
| idx = "((" + idx + " - 1) >= 0 ? (" + idx + " - 1) : (strlen(" + str + ") + " + idx + " - 1))"; | |||
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This change should not be done, as it slows down every index access, see above.
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Removed this. Thanks!
czgdp1807
approved these changes
Sep 23, 2022
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Fixes #1124