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- Updated the specs file not to reference the main.o files any more.

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- Clarified the caveats of the libm.a use.


git-svn-id: file:///Users/olsen/Code/migration-svn-zu-git/logical-line-staging/clib2/trunk@14904 87f5fb63-7c3d-0410-a384-fd976d0f7a62
This commit is contained in:
Olaf Barthel
2005-03-26 09:15:07 +00:00
parent aafda37c84
commit b1ac45a0b9
2 changed files with 33 additions and 17 deletions
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@ -71,21 +71,6 @@ other than the one that opened it. Also yet unsolved is the issue of reading
error codes from the <tt>errno</tt> variable which currently always contains the
error code left by the last caller.</p>
<p>Take care: thread-safety does not imply that you can have multiple callers
access and close the same file. There is no resource tracking to that degree
yet. All that the thread-safety tries to afford you is not to get into big trouble
if simultaneous and overlapping accesses to files, memory allocation and other
resources are taking place.</p>
<p> Also take care with file I/O involving the <tt>stdin</tt>/<tt>stdout</tt>/<tt>stderr</tt>
streams; read/write operations on these streams will be mapped to the <tt>Input()</tt>/</tt>Output()</tt>/<tt>ErrorOutput()</tt>
file handles of the process performing these operations. Since only this small set of
operations is mapped, functions such as <tt>fcntl()</tt> or <tt>select()</tt> will not
work on the <tt>stdin</tt>/<tt>stdout</tt>/<tt>stderr</tt> streams and the corresponding
file descriptors <tt>STDIN_FILENO</tt>/<tt>STDOUT_FILENO</tt>/<tt>STDERR_FILENO</tt>.
It is therefore strongly recommended to use the thread-safe library only for applications
which can cope with the limitations described above.</p>
<h2>3. What does it not do?</h2>
@ -157,6 +142,37 @@ library and the programs.</p>
<tt>GNUmakefile.68k</tt> for the 68k platform and <tt>GNUmakefile.os4</tt> for the AmigaOS4
PowerPC version.</p>
<h3>5.1 Floating point math and functions (<tt>scanf()</tt>, <tt>printf()</tt>, etc.) </h3>
<p>The plain <tt>libc.a</tt>, which your software would be linked against by default, does not contain
any floating point support code. This means, for example, that <tt>printf("%f",...)</tt> will not produce
the desired output and that <tt>scanf("%f",...)</tt> may not read any data at all. If your
program needs functions such as these or <tt>atod()</tt> then you must link against <tt>libm.a</tt> or
the equivalent.</p>
<p>To link the floating point support code with your software, use the <tt>-lm</tt> compiler option. Careful!
The order in which you specify the libraries to link against is important here. Thus, <tt>gcc -o test test.c -lm -lc</tt>
would correctly link the program <tt>test</tt> against the proper floating point math library, but
<tt>gcc -o test test.c -lc -lm</tt> would not.</p>
<h3>5.2 The thread-safe library</h3>
<p>Thread-safety does not imply that you can have multiple callers
access and close the same file. There is no resource tracking to that degree
yet. All that the thread-safety tries to afford you is not to get into big trouble
if simultaneous and overlapping accesses to files, memory allocation and other
resources are taking place.</p>
<p> Also take care with file I/O involving the <tt>stdin</tt>/<tt>stdout</tt>/<tt>stderr</tt>
streams; read/write operations on these streams will be mapped to the <tt>Input()</tt>/</tt>Output()</tt>/<tt>ErrorOutput()</tt>
file handles of the process performing these operations. Since only this small set of
operations is mapped, functions such as <tt>fcntl()</tt> or <tt>select()</tt> will not
work on the <tt>stdin</tt>/<tt>stdout</tt>/<tt>stderr</tt> streams and the corresponding
file descriptors <tt>STDIN_FILENO</tt>/<tt>STDOUT_FILENO</tt>/<tt>STDERR_FILENO</tt>.
It is therefore strongly recommended to use the thread-safe library only for applications
which can cope with the limitations described above.</p>
<h2>6. Conventions and design issues</h2>