This requires the makedef perl script by Derek, from the
c89-to-c99 repo. That scripts produces a .def file, listing
the symbols to be exported, based on the gcc version scripts
and the built object files.
To properly load non-function symbols from DLL files, the
data symbol declarations need to have the attribute
__declspec(dllimport) when building the calling code. (On mingw,
the linker can fix this up automatically, which is why it has not
been an issue so far. If this attribute is omitted, linking
actually succeeds, but reads from the table will not produce the
desired results at runtime.)
MSVC seems to manage to link DLLs (and run properly) even if
this attribute is present while building the library itself
(which normally isn't recommended) - other object files in the
same library manage to link to the symbol (with a small warning
at link time, like "warning LNK4049: locally defined symbol
_avpriv_mpa_bitrate_tab imported" - it doesn't seem to be possible
to squelch this warning), and the definition of the tables
themselves produce a warning that can be squelched ("warning C4273:
'avpriv_mpa_bitrate_tab' : inconsistent dll linkage, see previous
definition of 'avpriv_mpa_bitrate_tab').
In this setup, mingw isn't able to link object files that refer to
data symbols with __declspec(dllimport) without those symbols
actually being linked via a DLL (linking avcodec.dll ends up with
errors like "undefined reference to `__imp__avpriv_mpa_freq_tab'").
The dllimport declspec isn't needed at all in mingw, so we simply
choose not to declare it for other compilers than MSVC that requires
it. (If ICL support later requires it, the condition can be extended
later to include both of them.)
This also implies that code that is built to link to a certain
library as a DLL can't link to the same library as a static library.
Therefore, we only allow building either static or shared but not
both at the same time. (That is, static libraries as such can be,
and actually are, built - this is used for linking the test tools to
internal symbols in the libraries - but e.g. libavformat built to
link to libavcodec as a DLL cannot link statically to libavcodec.)
Also, linking to DLLs is slightly different from linking to shared
libraries on other platforms. DLLs use a thing called import
libraries, which is basically a stub library allowing the linker
to know which symbols exist in the DLL and what name the DLL will
have at runtime.
In mingw/gcc, the import library is usually named libfoo.dll.a,
which goes next to a static library named libfoo.a. This allows
gcc to pick the dynamic one, if available, from the normal -lfoo
switches, just as it does for libfoo.a vs libfoo.so on Unix. On
MSVC however, you need to literally specify the name of the import
library instead of the static library.
Signed-off-by: Martin Storsjö <martin@martin.st>
Add a configure function to pull in a compat object and set up
redirects in one operation. This avoids duplicating conditions
across configure and makefiles.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Make av_pix_fmt_descriptors table static on next major bump.
Making the table public is dangerous, since the caller has no way to
know how large it actually is. It also prevents adding new fields to
AVPixFmtDescriptor without a major bump.
The current API where the plain size is exposed is not of much
use - in most cases it is allocated dynamically anyway.
If allocated e.g. on the stack via an uint8_t array, there's no
guarantee that the struct's members are aligned properly (unless
the array is overallocated and the opaque pointer within it
manually aligned to some unspecified alignment).
Signed-off-by: Martin Storsjö <martin@martin.st>
- make tables static const
- remove useless use of compound literal
- break long lines
- fix a comma/semicolon typo
Signed-off-by: Mans Rullgard <mans@mansr.com>
The const qualifier is still removed although it happens inside
the strtol() function so no warning is generated.
Fixes:
libavutil/parseutils.c:110:11: warning: assignment discards qualifiers from pointer target type
Signed-off-by: Mans Rullgard <mans@mansr.com>
An alpha specifier outside the valid range results in a conversion from
double to long with undefined result. Range-checking the double and
only converting it after it passes avoids this.
Fixes fate-parseutils errors on some systems.
Signed-off-by: Mans Rullgard <mans@mansr.com>
ff_get_cpu_flags_x86() requires cpuid(), which is conditionally defined
elsewhere in the file. Surrounding the function body with ifdefs allows
building even when cpuid is not defined. An empty cpuflags mask is
returned in this case.
Now that there is CPU detection in YASM, there will always be one of
inline or external assembly enabled, which obviates the need to fall
back on CPU detection through compiler intrinsics.
There are cases where strncpy() does exactly what is required.
A blanket ban forces more convoluted solutions to be used in those
cases and has been a cause of bugs.
Signed-off-by: Mans Rullgard <mans@mansr.com>
All our ARM asm preserves alignment so setting this attribute
in a common location is simpler. This removes numerous warnings
when linking with armcc.
Signed-off-by: Mans Rullgard <mans@mansr.com>
LDR with register offset and PC as base register is not available in
the Thumb instruction set so the addition must be done separately.
Signed-off-by: Mans Rullgard <mans@mansr.com>
When building Thumb2 code, the end of a function, where the PIC
offsets are placed, need not be aligned. Although the values
are only accessed with instructions allowing unaligned addresses,
keeping them aligned is preferable.
Signed-off-by: Mans Rullgard <mans@mansr.com>
