compiler optimization
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The provenance memory model for C
[The wordpress markdown inclusion does a very bad job, it seems, there have been some idiotic formatting errors. I hope that these are fixed, now.] Continue reading
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Enforced bounds checking for frozen function interfaces
Many functions in the C library and other legacy codes have interfaces that don’t permit the current bounds checking syntax for array parameters, but that are frozen in time such that nobody will ever be able to change and improve them. In this example we go with but in fact any existing interface that has… Continue reading
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gcc doesn’t inline position independent code properly
When compiling position independent code, PIC, the gcc compiler fails to inline many functions that have an external name, that is that are not declared static. While this is conforming to the C standard, this is a complete blow to a lot of optimization efforts that I have put into my code in many places. Continue reading
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Effective types and aliasing
I already have posted about the evilness of cast some time ago, but recently I have seen that there is still much confusion out there about the C rules that pointer casts, also called type punning, break. So I will try to give it a more systematic approach, here. In fact, I think we should… Continue reading
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Demystify undefined behavior
In discussions about C or other standards (e.g POSIX) you may often have come across the term undefined behavior, UB for short. Unfortunately this term is sometimes mystified and even used to scare people unnecessarily, claiming that arbitrary things even outside the scope of your program can happen if a program “encounters undefined behavior”. (And… Continue reading
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inline functions as good as templates
I recently started to implement parts of the “Bounds checking interfaces” of C11 (Annex K) for P99 and observed a nice property of my implementation of qsort_s. Since for P99 basically all functions are inlined, my compilers (gcc and clang) are able to integrate the comparison functions completely into the sorting code, just as an… Continue reading
Jens Gustedt's Blog 