Hi Everyone/Bruno, I think Bruno and I were talking about this for a while back in 2018 or 2019. Gnulib was failing one self test due to floats on OS X 10.5 on PowerPC....
Here is the OS X man page on floats: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/float.3.html . The man page is wrong when it says "On PowerPC macs, by default the type long double is mapped to IEEE-754 double precision, described above." By default it maps to the 128-bit long doubles. It looks like -mlong-double-128 is engaged by default, and we need -mlong-double-64 to get to the behavior the man page details and Gnulib expects. $ cat test.c #include <stdio.h> #include <float.h> #include <stdint.h> int main(int argc, char* argv[]) { int lb[] = { LDBL_MANT_DIG, LDBL_MIN_EXP, LDBL_MAX_EXP, LDBL_DIG, LDBL_MIN_10_EXP, LDBL_MAX_10_EXP }; printf("sizeof(long double): %d\n", (int)sizeof(long double)); printf("LDBL_MANT_DIG: %d\n", lb[0]); printf("LDBL_MIN_EXP: %d\n", lb[1]); printf("LDBL_MAX_EXP: %d\n", lb[2]); printf("LDBL_DIG: %d\n", lb[3]); printf("LDBL_MIN_10_EXP: %d\n", lb[4]); printf("LDBL_MAX_10_EXP: %d\n", lb[5]); } $ gcc -O1 test.c -o test.exe $ ./test.exe sizeof(long double): 16 LDBL_MANT_DIG: 106 LDBL_MIN_EXP: -968 LDBL_MAX_EXP: 1024 LDBL_DIG: 31 LDBL_MIN_10_EXP: -291 LDBL_MAX_10_EXP: 308 $ gcc -O1 -mlong-double-128 test.c -o test.exe $ ./test.exe sizeof(long double): 16 LDBL_MANT_DIG: 106 LDBL_MIN_EXP: -968 LDBL_MAX_EXP: 1024 LDBL_DIG: 31 LDBL_MIN_10_EXP: -291 LDBL_MAX_10_EXP: 308 $ gcc -O1 -mlong-double-64 test.c -o test.exe $ ./test.exe sizeof(long double): 8 LDBL_MANT_DIG: 53 LDBL_MIN_EXP: -1021 LDBL_MAX_EXP: 1024 LDBL_DIG: 15 LDBL_MIN_10_EXP: -307 LDBL_MAX_10_EXP: 308 I don't know if something should be done proactively. Should Gnulib fail to configure without -mlong-double-64? Or maybe, should Gnulib just add -mlong-double-64 when needed? Jeff
