Commit 0d31ccdd authored by Committed by Marge Bot
[linker, macho] Don't map/allocate zero size sections and segments
Zero size sections are common even during regular build on MacOS. For instance: ``` $ ar -xv libHSghc-prim-0.6.1.a longlong.o $ otool -l longlong.o longlong.o: Mach header magic cputype cpusubtype caps filetype ncmds sizeofcmds flags 0xfeedfacf 16777223 3 0x00 1 2 176 0x00002000 Load command 0 cmd LC_SEGMENT_64 cmdsize 152 segname vmaddr 0x0000000000000000 vmsize 0x0000000000000000 <-- segment size = 0 fileoff 208 filesize 0 maxprot 0x00000007 initprot 0x00000007 nsects 1 flags 0x0 Section sectname __text segname __TEXT addr 0x0000000000000000 size 0x0000000000000000 <-- section size = 0 offset 208 align 2^0 (1) reloff 0 nreloc 0 flags 0x80000000 reserved1 0 reserved2 0 cmd LC_BUILD_VERSION cmdsize 24 platform macos sdk 10.14 minos 10.14 ntools 0 ``` The issue of `mmap`ing 0 bytes was resolved in !1050, but the problem remained. These 0 size segments and sections were still allocated in object code, which lead to failed `ASSERT(size > 0)` in `addProddableBlock` further down the road. With this change zero size segments **and** sections are not mapped/allocated at all. Test plan: 1. Build statically linked GHC. 2. Run `ghc --interactive`. Observe that REPL loads successfully (which was not the case before). 3. Load several more compiled hs files into repl. No failures.
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