Add a note about unintended _main symbol generation. #160
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| @@ -52,6 +52,8 @@ $ swiftc -target armv7-none-none-eabi -enable-experimental-feature Embedded -wmo | |||
| input1.swift input2.swift ... -c -o output.o | |||
| ``` | |||
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| > Note: Passing only a single `.swift` file to swiftc results in the generation of a `_main` symbol. During linking, this symbol could potentially clash with other objects that also define one. To avoid this, compile multiple Swift files together or use the `-parse-as-library` flag. | |||
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Shall we change _main to main? IIRC, the underscore is only present in Mach-O object files and it's probably more common to use Embedded Swift with ELF targets.
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It doesn't feel like this explanation is strictly correct (though im not sure). I thought swiftc always ran in "script" mode when -parse-as-library is omitted?
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@kubamracek You're right regarding the _ not being present for ELF. How about the following to cover both cases?
results in the generation of a
_main(Mach-O targets) ormain(ELF) symbol
@rauhul You mean that it shouldn't make a difference if one or two input files are used (regarding generation of main)? It does make a difference in my tests:
$ swiftc -enable-experimental-feature Embedded -wmo -c -o output.o first.swift && nm output.o | rg main
0000000000000000 T _main
$ swiftc -enable-experimental-feature Embedded -wmo -c -o output.o first.swift second.swift && nm output.o | rg main
If that's not what you meant, just let me know which part of the sentence you want me to fix.
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well im just also not sure about the precise behavior so it would be nice to have @artemcm or someone else more familiar with the driver make sure the documentation is correct
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