libc-test is developed as part of the musl project
http://www.musl-libc.org/

configuring:
	edit config.mak
build and run tests:
	make
clean up:
	make clean

make builds all test binaries and runs them to create
a REPORT file that contains all build and runtime errors
(this means that make does not stop at build failures)

contributing tests:

design goals:

- tests should be easy to run and build even a single test in isolation
(so test should be self contained if possible)
- failure of one test should not interfere with others
(build failure, crash or unexpected results are all failures)
- test output should point to the cause of the failure
- test results should be robust
- the test system should have minimal dependency
(libc, posix sh, gnu make)
- the test system should run on all archs and libcs
- tests should leave the system in a clean state

conventions:

each test is in a separate file at a path like src/directory/file.c with
its own main

the test should return 0 on success and non-0 on failure, on failure it
should print error messages to standard out if possible, on success no
message should be printed

to help with the above test protocol use t_error function for printing
errors and return t_status from main, see src/common/test.h
(t_error allows standard printf formatting, outputs at most 512bytes
in a single write call to fd 1, so there is no buffering, long outputs
are truncated, it sets the global t_status to 1)

it is common to do many similar checks in a test, in such cases macros
may be used to simplify the code like
#define T1(a,b) (check(a,b) || (t_error("check(%s,%s) failed\n", a, b),0))
#define T2(f,w) (result=(f), result==(w) || (t_error("%s failed: got %s, want %s\n", #f, result, w),0))

directories:

src/api: interface tests, build time include header tests
src/common: common utilities compiled into libtest.a
src/functional: functional tests aiming for large coverage of libc
src/math: tests for each math function with input-output test vectors
src/regression: regression tests aiming for testing particular bugs

initial set of functional tests are derived from the libc-testsuit of
Rich Felker, regression tests should contain reference of the bug
(musl commit hash, glibc bug tracker url, etc)

build system:

the targets src/directory/all and src/directory/clean build and clean
only the specified directory, each directory has its own Makefile that
invokes the top level make with src/directory/foo for the foo target,
so it is possible to work only under a specific test directory

the build and runtime errors of each target are accumulated into a
target.err file and in the end they are concatenated into a REPORT

each .c file in src/functional and src/regression are built into a
dynamic linked and a static linked executable test binary by default,
this behaviour can be changed by a similarly named .mk file changing
make variables and specifying additional rules:

$(N) is the name of the binary target (the file name without the .c)
$(N)-static is the name of the static binary target
$(D) is the directory
$(N).CFLAGS are added to the CFLAGS at compilation
$(N).LDFLAGS are added to the LDFLAGS at linking
$(N).LDLIBS are added to the LDLIBS at linking
$(N).BINS are the targets (if empty no binaries are built)
$(N).LIBS are the non-executable targets (shared objects may use it)

if a binary is linked together from several .o files then they
have to be specified as prerequisits for the binary targets and
added to the $(N).LDLIBS as well

if a binary depends on a file at runtime (eg. a .so opened by dlopen)
then the $(N).err target should depend on that file