diff options
| author | Jon Turney <jon.turney@dronecode.org.uk> | 2017-03-06 17:45:40 +0000 |
|---|---|---|
| committer | Jon Turney <jon.turney@dronecode.org.uk> | 2017-12-08 12:09:18 +0000 |
| commit | c6f14b3c81f5a40317452625ef8d56c2612fe776 (patch) | |
| tree | 350b9e28c1ec8cd292790f620778b099746a5e67 | |
| parent | 2ce4e1e5ad5b694a729e5df13cccaaf514abad45 (diff) | |
cygwin: Improve discussion of linker library ordering in faq-programming
Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>
| -rw-r--r-- | winsup/doc/faq-programming.xml | 37 |
1 files changed, 36 insertions, 1 deletions
diff --git a/winsup/doc/faq-programming.xml b/winsup/doc/faq-programming.xml index c0ddd7902..65bfed97e 100644 --- a/winsup/doc/faq-programming.xml +++ b/winsup/doc/faq-programming.xml @@ -876,10 +876,45 @@ example, single-stepping from these signals may not work as expected. <para>A common error is to put the library on the command line before the thing that needs things from it. </para> + <para>This is wrong <literal>gcc -lstdc++ hello.cc</literal>. This is right <literal>gcc hello.cc -lstdc++</literal>. </para> -</answer></qandaentry> + +<para> + The first command above (usually) works on Linux, because: + <itemizedlist mark="bullet"> + <listitem>A DT_NEEDED tag for libstdc++ is added when the library name is seen.</listitem> + <listitem>The executable has unresolved symbols, which can be found in libstdc++.</listitem> + <listitem>When executed, the ELF loader resolves those symbols.</listitem> + </itemizedlist> +</para> + +<para> + Note that this won't work if the linker flags <literal>--as-needed</literal> + or <literal>--no-undefined</literal> are used, or if the library being linked + with is a static library. +</para> + +<para> + PE/COFF executables work very differently, and the dynamic library which + provides a symbol must be fully resolved <emphasis>at link time</emphasis> + (so the library which provides a symbol must follow a reference to it). +</para> + +<para> + See point 3 in <xref linkend="faq.programming.unix-gui"></xref> for more + discussion of how this affects plugins. +</para> + +<para> + This also has consequences for how weak symbols are resolved. See <ulink + url="https://cygwin.com/ml/cygwin/2010-04/msg00281.html"></ulink> for more + discussion of that. +</para> + +</answer> +</qandaentry> <qandaentry id="faq.programming.stat64"> <question><para>Why do I get an error using <literal>struct stat64</literal>?</para></question> |