I installed AMD64 Ubuntu 16.04 LTS on another computer so that I could play. But it turns out that the same problem is in Fedora 24 so I needn't have bothered. Aside: I learned that the best description of my Canadian Bilingual Keyboard is under French(Canada) ; English-something-or-other. I'm still playing with this, but here are my preliminary observations. So here's the fundamental problem. "exp" is kind of like a reserved word in C. It is the exponential function and is declared in math.h. logo.h has #define exp expresn This screws up math.h. [language lawyer mode] The C standard as of N1548 (draft from 2010 December 2) says: 7.1.2 Reserved identifiers ... - All identifiers with external linkage in any of the following subclauses (including the future library directions) and errno are always reserved for use as identifiers with external linkage. 184) ... A following subclause includes a definition of exp. As I understand it, as an identifier with external linkage. As I read that, logo.h is NOT impinging since it is using exp as a macro name, something that gets "washed out" by the preprocessor, long before external linkages are understood. But the definition of exp affects the tricky code in /usr/include/x86_64-linux-gnu/bits/mathcalls.h __MATHCALL_VEC (exp,, (_Mdouble_ __x)); => __MATHCALL_VEC (expresn,, (_Mdouble_ __x)); which then malfunctions. Math.h: /* The file <bits/mathcalls.h> contains the prototypes for all the actual math functions. These macros are used for those prototypes, so we can easily declare each function as both `name' and `__name', and can declare the float versions `namef' and `__namef'. */ #define __SIMD_DECL(function) __CONCAT (__DECL_SIMD_, function) #define __MATHCALL_VEC(function, suffix, args) \ __SIMD_DECL (__MATH_PRECNAME (function, suffix)) \ __MATHCALL (function, suffix, args) and so on. I *think* that this is a bug in glibc (i.e. a "contract violation" of the C Standard), but I'm not 100% sure. Why does ucblogo have this definition? Here's my guess. UCB Logo uses a global variable with the name "exp" pervasively. Then it turned out that this was the (external linkage) name of the exp function. So there was a clash, even though the exp function isn't used by ucblogo. The #define was a simple way of renaming the global variable's external name without editing the source code. An effective hack. Fix? Several, but untested. 1. Brutish of brute force: Replace every #include <math.h> with #undef exp #include <math.h> #define exp expresn 2. Better fix: fix glibc to not take names that don't belong to it. 3. Blame the victim fix: in UCB Logo, replace every "exp" with "expresn" (or some other apt short name). 4. Simpler UCB Logo fix: Move the <> includes before the "" includes. Generally considered good style anyway. There is a chance that logo.h includes things that intentionally modify system headers. In that case, this fix will break these modifications.