aspx.cs page 3 of 9 CPPFLAGS indicates LDFLAGS indicates in Java Receive barcode pdf417 in Java CPPFLAGS indicates LDFLAGS indicates

CPPFLAGS indicates LDFLAGS indicates use none none writer toconnect none on nonegenerate code 39 nonstandard include paths with additional -I flags Java programming language nonstandard library directories with additional -L flags Let s look a none none t an example. Suppose that you are an unprivileged user on a university network, trying to build an open source project named Homer, which uses the. Understanding Errors and Warnings GNU build to none none ols. You run the configure script, and it informs you that it requires a particular development library named Marge. You track down the source for the Marge library which, luckily, is another GNU build project.

Because you are an unprivileged user, you cannot simply install the Marge library using the default installation settings. You have to install it under your home directory, so you choose to install it in ~/usr/local/lib. The entire process for building the Marge library would look something like this:.

$ configure -prefix=~/usr $ make $ make install Now to build none for none the Homer project, you have to inform Homer s configure script where to find the Marge library. You do this with the LDFLAGS environment variable, as follows:12. $ LDFLAGS="-L ~/usr/lib" ./configure Typically, a none none development library provides header files that you need to build code that uses the library. The compiler needs to know where to find these files. Given the prefix from before, Marge s include files would reside in ~/usr/include.

You should indicate this via the CPPFLAGS environment variable, as follows:. $ LDFLAGS="-L ~/usr/lib" CPPFLAGS="-I ~/usr/include" ./configure Notice that none none LDFLAGS contains options that are passed to the linker in this case, the -L option. Likewise, CPPFLAGS contains flags used by the preprocessor..

Errors during the Build Stage The job of t none for none he configure script is to check for all the required development tools and libraries, and depending on the project, it may generate the Makefile. An advantage of a project that uses the configure script to generate the Makefile is that the Makefile is not touched by human hands, so in theory, it should be free of syntax errors. You can identify such a project by looking at the distribution archive.

When the configure script generates the Makefile, the archive will not contain a Makefile; instead, it will have a file named

12. Note tha t the space before the tilde is required for the shell to expand it properly. The presence of the space requires the use of quotes to set the environment variables properly.

. 2 Building from Source Errors durin g the build can be broken into two categories: errors in the Makefile and errors detected during the build. 2.4.

3.1 Errors in the Makefile Although GNU build tools generate Makefiles that are unlikely to have syntax errors, there are ways to introduce syntax errors into an automatically generated Makefile. A developer can use the include keyword to insert text into the output Makefile verbatim, for example.

This presents an opportunity to introduce syntax errors into the output Makefile. If the project you are building is not using an automatically generated Makefile, you should consult any README files in the project to see what magic is required to build the project. Sometimes, developers use nondefault targets to build the project or require you to specify a variable on the command line manually.

It s usually safe to assume that the person packaging the source code made sure that it built before posting it on the Web. If you can t find a logical explanation for a syntax error in the Makefile, perhaps it s an indicator of the quality of the rest of the code. It may not be worth your time to continue in this case.


2 Errors Detected by make When your Makefile is free of syntax errors, any build errors will be in the commands section of the rules. make checks the return status of every command it executes and stops when it encounters an error. Developers can choose to ignore errors from specific commands, but this is the exception.

The errors you will see during a build can be broken down as shown in Table 2-8. I discuss compiler and linker errors in detail later; now I focus on the other category..

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