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Andres Freund authored
As clang currently doesn't support -fexcess-precision=standard, compiling x86-32 code with SSE2 disabled, can lead to problems with floating point overflow checks and the like. This issue was noticed because clang, on at least some BSDs, defaults to i386 compatibility, whereas it defaults to pentium4 on Linux. Our forced usage of __builtin_isinf() lead to some overflow checks not triggering when compiling for i386, e.g. when the result of the calculation didn't overflow in 80bit registers, but did so in 64bit. While we could just fall back to a non-builtin isinf, it seems likely that the use of 80bit registers leads to other problems (which is why we force the flag for GCC already). Therefore error out when detecting clang in that situation. Reported-By: Victor Wagner Analyzed-By: Andrew Gierth and Andres Freund Author: Andres Freund Discussion: https://postgr.es/m/20180905005130.ewk4xcs5dgyzcy45@alap3.anarazel.de Backpatch: 9.3-, all supported versions are affected
Andres Freund authoredAs clang currently doesn't support -fexcess-precision=standard, compiling x86-32 code with SSE2 disabled, can lead to problems with floating point overflow checks and the like. This issue was noticed because clang, on at least some BSDs, defaults to i386 compatibility, whereas it defaults to pentium4 on Linux. Our forced usage of __builtin_isinf() lead to some overflow checks not triggering when compiling for i386, e.g. when the result of the calculation didn't overflow in 80bit registers, but did so in 64bit. While we could just fall back to a non-builtin isinf, it seems likely that the use of 80bit registers leads to other problems (which is why we force the flag for GCC already). Therefore error out when detecting clang in that situation. Reported-By: Victor Wagner Analyzed-By: Andrew Gierth and Andres Freund Author: Andres Freund Discussion: https://postgr.es/m/20180905005130.ewk4xcs5dgyzcy45@alap3.anarazel.de Backpatch: 9.3-, all supported versions are affected
