Support for COMDAT sections for COFF output

Makefile.in

@@ -108,7 +108,7 @@ LIBOBJ_NW = stdlib/snprintf.$(O) stdlib/vsnprintf.$(O) stdlib/strlcpy.$(O) \
 	\
 	nasmlib/ver.$(O) \
 	nasmlib/alloc.$(O) nasmlib/asprintf.$(O) nasmlib/errfile.$(O) \
-	nasmlib/crc64.$(O) nasmlib/md5c.$(O) \
+	nasmlib/crc32.$(O) nasmlib/crc64.$(O) nasmlib/md5c.$(O) \
 	nasmlib/string.$(O) nasmlib/nctype.$(O) \
 	nasmlib/file.$(O) nasmlib/mmap.$(O) nasmlib/ilog2.$(O) \
 	nasmlib/realpath.$(O) nasmlib/path.$(O) \

Mkfiles/msvc.mak

@@ -72,7 +72,7 @@ LIBOBJ_NW = stdlib\snprintf.$(O) stdlib\vsnprintf.$(O) stdlib\strlcpy.$(O) \
 	\
 	nasmlib\ver.$(O) \
 	nasmlib\alloc.$(O) nasmlib\asprintf.$(O) nasmlib\errfile.$(O) \
-	nasmlib\crc64.$(O) nasmlib\md5c.$(O) \
+	nasmlib\crc32.$(O) nasmlib\crc64.$(O) nasmlib\md5c.$(O) \
 	nasmlib\string.$(O) nasmlib\nctype.$(O) \
 	nasmlib\file.$(O) nasmlib\mmap.$(O) nasmlib\ilog2.$(O) \
 	nasmlib\realpath.$(O) nasmlib\path.$(O) \

Mkfiles/openwcom.mak

@@ -61,7 +61,7 @@ LIBOBJ_NW = stdlib\snprintf.$(O) stdlib\vsnprintf.$(O) stdlib\strlcpy.$(O) &
 	&
 	nasmlib\ver.$(O) &
 	nasmlib\alloc.$(O) nasmlib\asprintf.$(O) nasmlib\errfile.$(O) &
-	nasmlib\crc64.$(O) nasmlib\md5c.$(O) &
+	nasmlib\crc32.$(O) nasmlib\crc64.$(O) nasmlib\md5c.$(O) &
 	nasmlib\string.$(O) nasmlib\nctype.$(O) &
 	nasmlib\file.$(O) nasmlib\mmap.$(O) nasmlib\ilog2.$(O) &
 	nasmlib\realpath.$(O) nasmlib\path.$(O) &

doc/nasmdoc.src

@@ -5896,6 +5896,44 @@ for data (and BSS) sections.
 Informational sections get a default alignment of 1 byte (no
 alignment), though the value does not matter.
 
+\b \I{comdat, win32 attribute}\c{comdat=}, followed by a number
+("selection"), colon (acting as a separator) and a name,
+marks the section as a \I{COMDAT section, in win32}"COMDAT section".
+It allows Microsoft linkers to perform function-level linking,
+to deal with multiply defined symbols, to eliminate dead code/data.
+The "selection" number should be one of the
+\c{IMAGE_COMDAT_SELECT_*} constants from
+\W{https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/Debug/pe-format.md#comdat-sections-object-only}\c{COFF format specification};
+this value controls if the linker allows multiply defined symbols
+and how it handles them.
+The name is the \I{COMDAT symbol, in win32}"COMDAT symbol"
+- basically a new name for the section. So even though you have one
+section given by the main name (e.g. \c{.text}), it can actually
+consist of hundreds of COMDAT sections having their own name
+(and alignment).
+When the "selection" is IMAGE_COMDAT_SELECT_ASSOCIATIVE (5),
+the following name is the "COMDAT symbol" of the associated COMDAT
+section; this way you can link a piece of code or data only when
+another piece of code or data gets actually linked.
+
+\> So, when linking a NASM-compiled file with some C code,
+the source may be structured as follows.
+Note that the default \c{.text} section in handled in a special
+way and it doesn't work well with \c{comdat}; you may want to append
+a \c{$} character and an arbitrary suffix to the section name.
+It will get linked into the \c{.text} section anyway - see the info on
+\W{https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/Debug/pe-format.md#grouped-sections-object-only}\c{Grouped Sections}.
+
+\c    section .text$1 align=16 comdat=1:FirstFnc
+\c       ...                                        ; Code linked only if referenced from C
+\c
+\c    section .text$1 align=16 comdat=1:SecondFnc
+\c       ...                                        ; Code linked only if referenced from C
+\c
+\c    section .rdata align=32 comdat=5:FirstFnc
+\c       ...                                        ; Data linked only if the related code (FirstFnc) is linked
+\c
+
 The defaults assumed by NASM if you do not specify the above
 qualifiers are:
 

include/hashtbl.h

@@ -79,6 +79,8 @@ static inline uint64_t crc64_byte(uint64_t crc, uint8_t v)
     return crc64_tab[(uint8_t)(v ^ crc)] ^ (crc >> 8);
 }
 
+uint32_t crc32b(uint32_t crc, const void *data, size_t len);
+
 void **hash_find(struct hash_table *head, const char *string,
 		struct hash_insert *insert);
 void **hash_findb(struct hash_table *head, const void *key, size_t keylen,

nasmlib/crc32.c

@@ -0,0 +1,115 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 1996-2021 The NASM Authors - All Rights Reserved
+ *   See the file AUTHORS included with the NASM distribution for
+ *   the specific copyright holders.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following
+ *   conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above
+ *     copyright notice, this list of conditions and the following
+ *     disclaimer in the documentation and/or other materials provided
+ *     with the distribution.
+ *
+ *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ *     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ *     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ *     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ *     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ *     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ *     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ *     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * ----------------------------------------------------------------------- */
+
+#include "compiler.h"
+#include "hashtbl.h"
+
+const uint32_t crc32_tab[256] = {
+    0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
+    0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
+    0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
+    0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
+    0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
+    0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
+    0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
+    0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
+    0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
+    0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
+    0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
+    0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
+    0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
+    0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
+    0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
+    0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
+    0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
+    0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
+    0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
+    0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
+    0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
+    0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
+    0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
+    0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
+    0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
+    0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
+    0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
+    0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
+    0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
+    0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
+    0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
+    0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
+    0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
+    0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
+    0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
+    0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
+    0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
+    0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
+    0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
+    0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
+    0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
+    0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
+    0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
+    0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
+    0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
+    0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
+    0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
+    0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
+    0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
+    0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
+    0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
+    0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
+    0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
+    0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
+    0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
+    0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
+    0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
+    0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
+    0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
+    0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
+    0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
+    0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
+    0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
+    0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
+};
+
+uint32_t crc32b(uint32_t crc, const void *data, size_t len)
+{
+    register const uint8_t *p = data;
+    register uint32_t hashval = crc;
+
+    while (len--)
+    {
+        hashval = (hashval >> 8) ^ crc32_tab[(hashval ^ *p++) & 0xff];
+    }
+
+    return hashval;
+};