Dear GCC Developers, I am unsuccessfully using g++ 12.0.4 to compile lengthy c++ codes. Those codes are automatically generated from my own code-generator tools that depend on parameters p. Typical applications are: - Taylor series of order p inserted into consistency conditions of numerical schemes, to determine optimal method parameters (think of, e.g., Runge-Kutta methods) - recursive automatic code transformation (think of adjoints of adjoints of adjoints...) of recursion level p - Hilbert curves or other space-filling curves to generate code that simulates cache utilization in a Monte-Carlo context I verify that for small p the codes compile and execute to the expected result. However, there is always a threshold for p so that the generated cpp file is so long that the compiler will just terminate after ~10min without monitor output but return the value +1. My cpp files range from 600k LOC up to 1Bio LOC. Often, the file comprises of one single c++ template class member function definition that relies on a few thousand lines of template-classes. I would like to know: 1) Am I doing something wrong in that GCC should be able to compile lengthy codes? 2) Is it known that GCC is unable to compile lengthy codes? 3) Is it acknowledged that a compiler's ability to compile large files is relevant? 4) Are possible roots known for this inability and are these deliberate? To give just one glimpse at the relevance: I analyzed methods for solving F(x)=0 by using k stages -DF(x)*vk= F(x+sum_i bki*vi). Compiling a Taylor series code with p=3, I was able to verify that three iterations of the Chord method converge of fourth order, thus surpassing Newton's method (same cost, but only quadratic order). Checking whether any four-stage method exists that converges of fifth order necessitates the compilation of a single cpp file function that is 1.2Mio lines of code long. Since 2018 I am occasionally trying to find a way to compile it. I also used this code to automatically generate Butcher-type tableaus for generalizations to initial-value problem solvers. One could really only dream of what scientific leaps become possible only if lengthy codes were compilable. Right now, whenever a situation of this kind occurs, I have to give up, cut my (possibly months of work) losses, and move on to working on something else -- because it seems there is nothing I can do about it. Even spitting a code of 1Bio LOC into chunks of 100k LOC and then automating to compile and link these in turn seems hopeless; and probably the linker has limitations as well.. But since this problem is to frequent to my life, I would really like to find out how to fix it once and for all. This is a problem that I have been suffering from severely for years because it basically cripples how I can put my mathematical expertise to use. Thank you for getting in touch. Kind regards, Kai
