Timeline for Shortest code to throw SIGILL
Current License: CC BY-SA 3.0
17 events
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| Jun 17, 2020 at 9:04 | history | edited | Community Bot |
Commonmark migration
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| Dec 26, 2017 at 13:12 | history | edited | Dennis | CC BY-SA 3.0 |
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| Dec 26, 2017 at 5:25 | comment | added | Peter Cordes |
Huh, that's weird that -z execstack also controls the .data section. I checked with x86-64 gcc7.1.1 on Arch Linux, and you're right that that @progbits directive makes the data section non-executable, and that -z execstack overrides it, and that the default (with no directive and no option) is an executable .data section. I guess execstack is more like executability for non-text segments in general.
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| Apr 13, 2017 at 12:39 | history | edited | Community Bot |
replaced http://codegolf.stackexchange.com/ with https://codegolf.stackexchange.com/
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| Nov 23, 2016 at 22:55 | history | edited | Dennis | CC BY-SA 3.0 |
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| Nov 21, 2016 at 20:57 | history | edited | Dennis | CC BY-SA 3.0 |
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| Nov 21, 2016 at 4:35 | comment | added | Peter Cordes |
Also note that 06 is only an invalid instruction in x86-64. In 32-bit mode, it's PUSH ES, so this answer only works with compilers that default to -m64. See ref.x86asm.net/coder.html#x06. The only byte sequence that's guaranteed to decode as an illegal instruction on all future x86 CPUs is the 2 byte UD2: 0F 0B. Anything else could be some future prefix or instruction-encoding. Still, upvoted for a cool way to get a C compiler to stick a main label on some bytes!
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| Nov 21, 2016 at 4:31 | comment | added | Peter Cordes |
I think it's pretty standard for executables for Unix-like systems to have text/data/bss segments. The linker places the .rodata section inside the text segment of the executable, and I expect this will be the case on pretty much any platform. (The kernel's program-loader only cares about segments, not sections).
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| Nov 20, 2016 at 19:40 | comment | added | zwol |
GCC will complain about main not being a function but only if you turn on the warnings (either -Wall or -pedantic will do it).
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| Nov 20, 2016 at 17:20 | history | edited | Dennis | CC BY-SA 3.0 |
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| Nov 20, 2016 at 16:58 | history | edited | Dennis | CC BY-SA 3.0 |
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| Nov 20, 2016 at 16:33 | history | edited | Dennis | CC BY-SA 3.0 |
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| Nov 20, 2016 at 16:32 | comment | added | Bobby Sacamano | @JackDobson it's undefined behavior, so it doesn't work in terms of C; you're at the compiler's mercy. Clang even has a warning for this for some reason: "variable named 'main' with external linkage has undefined behavior". | |
| Nov 20, 2016 at 16:24 | history | edited | Dennis | CC BY-SA 3.0 |
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| Nov 20, 2016 at 16:15 | comment | added | Mia yun Ruse |
Love the complete avoidance of even using a function :) How does this work in C terms, though? Does the compiler see that main is a 6 and try to call it (which I guess would make it give up and try the instruction)?
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| Nov 20, 2016 at 16:11 | history | edited | Dennis | CC BY-SA 3.0 |
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| Nov 20, 2016 at 16:05 | history | answered | Dennis | CC BY-SA 3.0 |