Cannabis is one of the most common mind-altering substances. It is used both medicinally and recreationally and is enmeshed in a complex and changing legal landscape. Anecdotal evidence suggests that some software developers may use cannabis to aid some programming tasks. At the same time, anti-drug policies and tests remain common in many software engineering environments, sometimes leading to hiring shortages for certain jobs. Despite these connections, little is actually known about the prevalence of, and motivation for, cannabis use while programming. In this paper, we report the results of the first large-scale survey of cannabis use by programmers. We report findings about 803 developers' (including 450 full-time programmers') cannabis usage prevalence, perceptions, and motivations. For example, we find that some programmers do regularly use cannabis while programming: 35% of our sample has tried programming while using cannabis, and 18% currently do so at least once a month. Furthermore, this cannabis usage is primarily motivated by a perceived enhancement to certain software development skills (such as brainstorming or getting into a programming zone) rather than medicinal reasons (such as pain relief). Finally, we find that cannabis use while programming occurs at similar rates for programming employees, managers, and students despite differences in cannabis perceptions and visibility. Our results have implications for programming job drug policies and motivate future research into cannabis use while programming.