On Tue, 30 Apr 2024, Martin Storsjö wrote:
On Mon, 29 Apr 2024, Pali Rohár wrote:
So based on these experiments when building library, I can conclude
that:
X = Y
is the same as:
Y == X
and it means that function named X in the source code is present in the
result DLL library under name Y.
So `foo = bar` is also renaming of the symbol, and not aliasing.
For completeness, what happens when both = and == are used at the same
line:
$ cat test.def
LIBRARY "test.dll"
EXPORTS
foo = func == bar
$ cat test.c
void func(void) { }
$ i686-w64-mingw32-gcc -shared test.c test.def -o test.dll
$ readpe -e test.dll
Exported functions
Library
Name: test.dll
Functions
Function
Ordinal: 1
Address: 0x1410
Name: bar
So line "X = Y == Z" has same meaning as "Y == Z" and so same as "Z =
X".
Such logic does not make sense for me, but whatever. It shows that
documentation is incomplete and ambiguous.
As far as I know, they're used in different circumstances. When linking a
DLL, you'd use the syntax "X = Y" to export a symbol under a different
name. MS link also supports this syntax for this purpose.
When creating an import library with dlltool, the == syntax is used with
the purpose of creating an import library with a symbol with one name,
pointing at a DLL export with a different name.
I see you only inspected the export table of the linked DLLs in your
experiment, but you also should create an import library at the same time
(-Wl,--out-implib) and inspect what symbols it provides - which hopefully
would link against the export names of the DLL that was created at the
same time.
It's probably also interesting to test and see what dlltool does with this
kind of def file.
// Martin
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