16.6 Troubleshooting Compiles and Installations
If you understand the difference between compiler errors, compiler warnings, linker errors, and shared library problems as described in Chapter 15, you shouldn’t have too much trouble fixing many of the glitches that arise when you’re building software. This section covers some common problems. Although you’re unlikely to run into any of these issues when building using autoconf, it never hurts to know what they look like.
Before covering specifics, make sure that you can read certain kinds of make output. It’s important to know the difference between an error and an ignored error. The following is a real error that you need to investigate:
make: *** [target] Error 1
However, some Makefiles suspect that an error condition might occur but know that these errors are harmless. You can usually disregard any messages like this:
make: *** [target] Error 1 (ignored)
Furthermore, GNU make often calls itself many times in large packages, with each instance of make in the error message marked with [N], where N is a number. You can often quickly find the error by looking at the make error that comes directly after the compiler error message. For example:
compiler error message involving file.c
make[3]: *** [file.o] Error 1
make[3]: Leaving directory '/home/src/package-5.0/src'
make[2]: *** [all] Error 2
make[2]: Leaving directory '/home/src/package-5.0/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/src/package-5.0/'
make: *** [all] Error 2
The first three lines here give you the information you need. The trouble centers around file.c, located in /home/src/package-5.0/src. Unfortunately, there’s so much extra output that it can be difficult to spot the important details. Learning how to filter out the subsequent make errors goes a long way toward helping you dig out the real cause.
16.6.1 Specific Errors
Here are some common build errors that you might encounter.
Problem
Compiler error message:
src.c:22: conflicting types for 'item'
/usr/include/file.h:47: previous declaration of 'item'
Explanation and fix
The programmer made an erroneous redeclaration of item on line 22 of src.c. You can usually fix this by removing the offending line (with a comment, an #ifdef, or whatever works).
Problem
Compiler error message:
src.c:37: 'time_t' undeclared (first use this function)
--snip--
src.c:37: parse error before '...'
Explanation and fix
The programmer forgot a critical header file. The manual pages are the best way to find the missing header file. First, look at the offending line (in this case, line 37 in src.c). It’s probably a variable declaration like the following:
time_t v1;
Search forward for v1 in the program for its use around a function call. For example:
v1 = time(NULL);
Now run man 2 time or man 3 time to look for system and library calls named time(). In this case, the section 2 manual page has what you need:
SYNOPSIS
#include <time.h>
time_t time(time_t *t);
This means that time() requires time.h. Place #include <time.h> at the beginning of src.c and try again.
Problem
Compiler (preprocessor) error message:
src.c:4: pkg.h: No such file or directory
(long list of errors follows)
Explanation and fix
The compiler ran the C preprocessor on src.c but could not find the pkg.h include file. The source code likely depends on a library that you need to install, or you may just need to provide the compiler with the nonstandard include path. Usually, you’ll just need to add a -I include path option to the C preprocessor flags (CPPFLAGS). (Keep in mind that you might also need a -L linker flag to go along with the include files.)
If it doesn’t look as though you’re missing a library, there’s an outside chance you’re attempting a compile for an operating system that this source code does not support. Check the Makefile and README files for details about platforms.
If you’re running a Debian-based distribution, try the apt-file command on the header filename:
$ apt-file search pkg.h
This might find the development package that you need. For distributions that use yum, you can try this instead:
$ yum provides */pkg.h
Problem
The make error message:
make: prog: Command not found
Explanation and fix
To build the package, you need prog on your system. If prog is something like cc, gcc, or ld, you don’t have the development utilities installed on your system. On the other hand, if you think prog is already installed on your system, try altering the Makefile to specify the full pathname of prog.
In rare cases with poorly configured source code, make builds prog and then uses prog immediately, assuming that the current directory (.) is in your command path. If your $PATH does not include the current directory, you can edit the Makefile and change prog to ./prog. Alternatively, you could append . to your path temporarily.