![]() Common examples include custom commands or as values for some target properties. A generator expression has the form $ and can be used in a variety of places. These typically arise from a misunderstanding of CMake’s quoting rules and argument processing. In the CMake forum, you will sometimes see posts asking why CMake doesn’t seem to recognize a particular generator expression. Message("With evaluation of $") Number of arguments: 1įor a more detailed discussion of passing arguments using variables, see Forwarding Command Arguments In CMake. As a special case, if the opening brackets are immediately followed by a newline, CMake discards that newline.You must match the same number of equal signs at the opening and closing brackets.Bracket syntax uses a pair of square brackets with zero or more equal signs between them.This can be useful when defining strings with CMake code that you don’t want evaluated immediately. CMake will also not substitute variables inside bracket-quoted values. This makes them very handy for defining regular expressions. CMake interprets values quoted with bracket syntax literally, so you do not need to escape quotes or backslashes. With CMake 3.0 or later, you can use lua-style bracket syntax instead of surrounding the value with double-quotes. You can express a value with embedded quotes more clearly by quoting the whole string and escaping the embedded quotes with a backslash: set(args "something=\"I contain spaces\"" anotherArg) Quoting With Bracket Syntax The output from the above would be: arg: something="unexpected perhaps" Set(args something="unexpected perhaps" anotherArg) # Relies on legacy behavior, don't do this You should avoid using unescaped quotes anywhere other than the start and end of a value. CMake’s documentation warns that this is legacy behavior. The quotes do still prevent spaces from acting as argument separators. If a value does not start with double-quotes, any double-quotes after the first character become part of the value. ![]() Some languages support quoting that starts part way through a value, but CMake’s handling of such arguments is different to most. add_library(MyThings STATIC someFile.cpp "I need quotes.cpp") Directory separators do not require quoting. However, you only need quotes if the file name contains whitespace or semicolons (and file names should never contain semicolons, since they would almost certainly lead to other problems). To demonstrate, the following are all equivalent: add_library(MyThings STATIC someFile.cpp)Īdd_library(MyThings STATIC "someFile.cpp")Īdd_library("MyThings" "STATIC" "someFile.cpp")ĭevelopers often feel the need to treat file names and paths specially, often adding quotes when not required. It is up to the command’s implementation to give those strings meaning as keywords. We might think of those as being special, but from CMake’s point of view, they too are just strings. In fact, much of the time, you can pass strings to commands without quoting. Unlike many scripting languages, CMake doesn’t always require strings to be quoted. Command Arguments From Substituted Content.This can be done by setting the IMPORTED_LOCATION property on your new library: set_property ( TARGET libcinder PROPERTY IMPORTED_LOCATION libcinder. Once you’ve defined the library, you then have to tell CMake where the prebuilt library is located. ![]() The third argument is the most important here - it tells CMake that this library is pre-built, and that there are therefore no sources to specify. You can do this with the add_library command: add_library ( libcinder STATIC IMPORTED ) To link to a third-party library, you first need to add the library to your project as if it were a library you are building yourself. Same syntax as above, but use the link_directories command instead: link_directories (. external/boost/ )Īdding a Directory to your Library Search Paths To add a header search path, use the include_directories command. Enjoy!Īdding a Directory to your Header Search Paths I thought it would be useful to combine all of these little tips into a single post. During this process, there were several tasks that required some Googling (as the CMake documentation can be a bit hard to chew). In my last post I explained how I recently extended my build to support multiple platforms using CMake.
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