Process-wide locale changed at runtime
ID |
c.correctness.global_locale_mutation |
Severity |
low |
Remediation Complexity |
medium |
Remediation Risk |
medium |
Remediation Effort |
medium |
Resource |
Concurrency |
Language |
C / C++ |
Description
Reports a call that changes the process-wide global locale: setlocale with a non-null locale argument, or std::locale::global.
Rationale
Both setlocale and std::locale::global change locale-dependent behavior — number and date formatting, string collation, character classification, and more — for the entire process, including every other thread and every library the program links against. Neither call is thread-safe with concurrent use of locale-sensitive functions, so a mutation racing with formatting or parsing elsewhere is undefined behavior, and even single-threaded, the effect is a hidden global side effect that any later locale-dependent call now depends on.
The following code illustrates the pattern detected by this rule:
void set_c_locale(void)
{
// FLAGGED: Process-wide locale changed at runtime
setlocale(LC_ALL, "");
}Remediation
Prefer locale objects scoped to where they are needed: construct a std::locale and pass it explicitly to the stream, facet, or function that needs it, instead of mutating the global locale. If a process-wide locale is genuinely required, set it once during single-threaded startup before any other thread can observe or race the change.