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V1078. An empty container is iterated. The loop will not be executed.
The analyzer has detected an attempt to iterate an empty container. As a result, not a single iteration of the loop will occur. This may indicate an error.
Let's look at the example that may be the result of unsuccessful refactoring:
#include <vector>
#include <string_view>
std::vector<std::string_view> GetSystemPaths()
{
std::vector<std::string_view> paths;
#ifdef _WIN32
paths.emplace_back("C:/Program files (x86)/Windows Kits");
paths.emplace_back("C:/Program Files (x86)/Microsoft Visual Studio");
#elif defined(__APPLE__)
paths.emplace_back("/Applications");
paths.emplace_back("/Library");
paths.emplace_back("/usr/local/Cellar");
#elif defined(__linux__)
// TODO: Don't forget to add some specific paths
#endif
return paths;
}
bool IsSystemPath(std::string_view path)
{
static const auto system_paths = GetSystemPaths();
for (std::string_view system_path : system_paths)
{
if (system_path == path)
{
return true;
}
}
return false;
}The content of the 'system_paths' container depends on the operating system for which the application is compiled. For Linux and all other systems except Windows and macOS, an empty container is obtained as a result of the preprocessor directives expansion.
In the context of this example, this is an undesirable behavior of the 'GetSystemPaths' function. In the case of Linux, to fix the warning, a developer needs to add the necessary paths. When compiling to a new operating system (for example, FreeBSD) a developer may need to handle an error with static_assert. Here is the example of safe code:
#include <vector>
#include <string_view>
std::vector<std::string_view> GetSystemPaths()
{
std::vector<std::string_view> paths;
#ifdef _WIN32
....
#elif defined(__APPLE__)
....
#elif defined(__linux__)
paths.emplace_back("/usr/include/");
paths.emplace_back("/usr/local/include");
#else
static_assert(false, "Unsupported OS.");
#endif
return paths;
}In general, if an empty container iteration was the programmer's intent, then the warning can be suppressed.
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