I am running C code compiled and linked in two different configurations of the same 'project' with exactly the same settings (source/header files, include directories, libraries, additional dependencies, etc.). The two configurations are 'Debug' and 'float'; both are in floating point arithmetic, which is selected in preprocessing (a macro that selects fixed or floating point arithmetic is not defined, leading to compiling/linking in floating point). The numerical results differ between the two runs; e.g., an array element that is a complex-number structure (with two float members---real and imag) shows significantly different numeric values after the two runs.

Has anybody come across a similar problem? I would appreciate any insight, or suggestions for where to look---thank you in advance.