Optimize liblzma.a build

[NobodyXu]

• Reduce liblzma.a size by using --gc-sections
• Add new feat fat-lto and thin-lto to turn out fat and thin lto for building liblzma.a
• Add new feat thin to optimize for size using macro HAVE_SMALL

Signed-off-by: Jiahao XU Jiahao_XU@outlook.com

[NobodyXu]

The CI seems to be broken by new feature thin:

  running: "cc" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-4" "-fno-omit-frame-pointer" "-m64" "-I" "xz-5.2/src/liblzma/api" "-I" "xz-5.2/src/liblzma/lzma" "-I" "xz-5.2/src/liblzma/lz" "-I" "xz-5.2/src/liblzma/check" "-I" "xz-5.2/src/liblzma/simple" "-I" "xz-5.2/src/liblzma/delta" "-I" "xz-5.2/src/liblzma/common" "-I" "xz-5.2/src/liblzma/rangecoder" "-I" "xz-5.2/src/common" "-I" "/home/runner/work/xz2-rs/xz2-rs/lzma-sys" "-Wall" "-Wextra" "-std=c99" "-pthread" "-ffunction-sections" "-fdata-sections" "-fmerge-all-constants" "-Wl,--gc-sections" "-flto" "-DHAVE_CONFIG_H=1" "-DHAVE_SMALL=1" "-o" "/home/runner/work/xz2-rs/xz2-rs/target/debug/build/lzma-sys-817308151459d6e7/out/xz-5.2/src/liblzma/check/crc64_fast.o" "-c" "xz-5.2/src/liblzma/check/crc64_fast.c"
  cargo:warning=xz-5.2/src/liblzma/check/crc64_fast.c: In function ‘lzma_crc64’:
  cargo:warning=xz-5.2/src/liblzma/check/crc64_fast.c:40:31: error: ‘lzma_crc64_table’ undeclared (first use in this function); did you mean ‘lzma_crc32_table’?
  cargo:warning=   40 |                         crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);
  cargo:warning=      |                               ^~~~~~~~~~~~~~~~
  cargo:warning=      |                               lzma_crc32_table
  cargo:warning=xz-5.2/src/liblzma/check/crc64_fast.c:40:31: note: each undeclared identifier is reported only once for each function it appears in

This is probably an upstream bug, since HAVE_THIN disables lzma_crc64_table and only keeps lzma_crc32_table here:

#ifdef HAVE_SMALL
extern uint32_t lzma_crc32_table[1][256];
extern void lzma_crc32_init(void);
#else
extern const uint32_t lzma_crc32_table[8][256];
extern const uint64_t lzma_crc64_table[4][256];
#endif

[NobodyXu]

I think upgrading xz to latest v5.4.1 might fix this.

[NobodyXu]

I think #108 might fix the error in this PR, so I would retry after that PR is merged.

[wcampbell0x2a]

This should be gates behind OPT_LEVEL. Only after OPT_LEVEL = Some("3")?

[wcampbell0x2a]

Related to this MR by name.... xz2 should also define NDEBUG when OPT_LEVEL is 3

https://github.com/xz-mirror/xz/blob/b69da6d4bb6bb11fc0cf066920791990d2b22a06/dos/config.h#L136

[NobodyXu]

Related to this MR by name.... xz2 should also define NDEBUG when OPT_LEVEL is 3

I've added #define NDEBUG 1 to config.h.

[NobodyXu]

This should be gates behind OPT_LEVEL. Only after OPT_LEVEL = Some("3")?

I'm not sure which line are you referring to.
The line you referenced does not contain anything related to opt-level or optimization flags.