There are more compiler bugs than many ever think. From mainframe COBOL compilers to gcc, I have encountered bugs in programs that were a result of what the com

There are more compiler bugs than many ever think. From mainframe COBOL compilers to gcc, I have encountered bugs in programs that were a result of what the compiler did. The original source code did nothing special - it was simple code and due to specific optimisations that the compiler performed, inexplicable seemingly random errors would arise. One would have to constrain the optimisations the compiler would do to get the code to execute correctly. No compiler is bug free. The bugs can manifest in strange ways and sometimes they will manifest only on specific kinds of data (edge case data). Certainly there are many programs that are written incorrectly and give rise to apparently inexplicable errors that are due to misunderstood language features or specified compiler limits. However, there are also many programs that do not have such source code errors that end up being rewritten in some way to avoid compiler based errors. The worst I have seen is when dummy statements have to be put in to the source code in order to get the program to work correctly. I have seen compilers change the precision of numbers from one version to the next and you have to add additional code to restrict those numbers back to the specified range. I have seen compilers allocate multiple i/o buffers as an optimisation that causes a program to fail when a single i/o buffer allocation works fine - one has to turn off the optimisation - no documentation available as to how the compiler generated code uses those buffers. All I can say is that it takes a fair amount of investigation to determine what kind of bug it is when it is subtle and randomly occurring. It can be everything from errors in the source to errors in the libraries to errors in code generation to errors in the o/s (including driver errors or memory errors). Anyone who blanket says the compiler is not to blame is living in a rose coloured glasses world. Compilers are complex programs and the source code for them can be just as wrong as for any other program. The code generated for compilers can be just as bug ridden as any other program.