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interp: keep memcpy results out of the global state when an initializer is reverted - #5904
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davecheney merged 1 commit intoOct 19, 2026
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Please rebase and resolve merge conflicts @davecheney thank you. |
…er is reverted When interp reverts a package initializer and runs it at run time, a memcpy or memmove that interp already evaluated must not change the initial value of the destination. getWritable put its clone in the runner's global object table instead of in the current memory view, so the copy stayed in the initial value after the revert, and the initializer then did the copy again at run time. For example, an initializer that does copy(data[1:], data[:3]) on "ABCD" and then calls println in a function with a defer gives "AAAB" instead of "AABC". The same program gives the correct result when it runs from main, and the 0.43.0 release has the same problem. getWritable has done this since the interp rewrite in 30df912. The problem was found during review of tinygo-org#5903, which lets interp evaluate functions with defer. This change does not depend on tinygo-org#5903.
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@deadprogram rebased, PTAL |
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Thanks @davecheney for tracking this one down. I ran the tests on my local machine. Working as expected, thank you very much!
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…er is reverted (tinygo-org#5904) When interp reverts a package initializer and runs it at run time, a memcpy or memmove that interp already evaluated must not change the initial value of the destination. getWritable put its clone in the runner's global object table instead of in the current memory view, so the copy stayed in the initial value after the revert, and the initializer then did the copy again at run time. For example, an initializer that does copy(data[1:], data[:3]) on "ABCD" and then calls println in a function with a defer gives "AAAB" instead of "AABC". The same program gives the correct result when it runs from main, and the 0.43.0 release has the same problem. getWritable has done this since the interp rewrite in 30df912. The problem was found during review of tinygo-org#5903, which lets interp evaluate functions with defer. This change does not depend on tinygo-org#5903.
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When interp reverts a package initializer and runs it at run time, a memcpy or memmove that interp already evaluated must not change the initial value of the destination. getWritable put its clone in the runner's global object table instead of in the current memory view, so the copy stayed in the initial value after the revert, and the initializer then did the copy again at run time. For example, an initializer that does copy(data[1:], data[:3]) on "ABCD" and then calls println in a function with a defer gives "AAAB" instead of "AABC". The same program gives the correct result when it runs from main, and the 0.43.0 release has the same problem. getWritable has done this since the interp rewrite in 30df912.
The problem was found during review of #5903, which lets interp evaluate functions with defer. This change does not depend on #5903.