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20 lines
950 B
TeX
20 lines
950 B
TeX
\newpage
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\subsection{Unorthodox Control Flow}
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In \lC, the \texttt{setjmp.h} header file can be included, which gives us access to \texttt{setjmp} and \texttt{longjmp}.
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To use them, we first need to declare a \texttt{jmp\_buf} somewhere, usually as a static variable.
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The \texttt{setjmp( jmp\_buf env } function stores the current stack / environment in the \texttt{jmp\_buf} and returns 0.
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The \texttt{longjmp( jmp\_buf env, int val )} function causes a second return, which returns \texttt{val},
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to the \texttt{setjmp} invocation and jumps back to that place.
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\inputcodewithfilename{c}{}{code-examples/01_asm/08_unorthodox-controlflow.c}
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What the above code outputs is: \texttt{second} followed by \texttt{main}.
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\newpage
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They are implemented in Assembly as follows. Nothing really surprising for the implementation there.
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The assembly code is from the Musl \lC\ library
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\inputcodewithfilename{gas}{}{code-examples/01_asm/09_setjmp-longjmp.s}
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