Add interrupt instruction for games to print to terminal #1947
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src/ARMInterpreter.cpp
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| u32 c; | ||
| cpu->DataRead8(addr++, &c); | ||
| if (!c) break; | ||
| printf("%c", c); |
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Please use Platform::Log instead of printf. Then the output can go wherever the frontend wants it to instead of always stdout.
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Is there actually any homebrew out there that uses this over nocash prints? |
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This is more helpful for rom-hacking and decompilation, where you'd have the ability to insert arbitrary print statements. Additionally, as far as I'm aware, Desmume does not support the nocash debug registers. It would be nice to have a printing mechanism that works across both emulators. |
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Just following up, are there any concerns with merging in this feature? |
nadiaholmquist
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Sorry to keep bugging, is it okay to merge this? |
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I would suggest that if this feature will be added it should be an opt-in feature to avoid clashing with possible other uses of this swi. E.g. someone can map vectors to itcm and have their own swi handler. It's rare, but possible (for example in gbarunner3). Personally I think the existing way to print with no$ IO registers is less intrusive in that regard. |
| @@ -266,6 +266,22 @@ void A_MRC(ARM* cpu) | |||
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| void A_SVC(ARM* cpu) | |||
| { | |||
| // Print from game. Execute `svc 0xFC` with the null-terminated string address in `r0`. | |||
| if ((cpu->CurInstr & 0xFF) == 0xFC && cpu->NDS.GetDebugPrint()) | |||
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I tried ((cpu->CurInstr >> 16) & 0xFF) as suggested, but this didn't work in practice. The interrupt instruction (swi 0xFC) was compiled to the following:
8: ef0000fc svc 0x000000fc
If the game executes
svc 0xFC, the contents of the null-terminated string addressed in registerr0will be printed to the terminal.For consistency, this is the same mechanism that is used in Desmume (source).