# "Entry point crc32\_z not found in gvc.dll" **URL:** \ **Category:** Dev\ **Created:** [January 29, 2025, 4:01pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684 "2025-01-29T16:01:44Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![sprezzatura](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/sprezzatura/32/1815_2.png) [@sprezzatura](https://forum.graphviz.org/u/sprezzatura)\ **Post date:** [January 29, 2025, 4:01pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/1 "2025-01-29T16:01:44Z")
I am getting the error “The procedure entry point crc32\_z could not be located in dynamic library gvc.dll” when attempting to run my program. I am running Windows 10, linking to Graphviz 12.2.1 lib’s, 64-bit. Compiling with MSVC 2017. I am using the pre-compiled files, I don’t have the source and I did not compile it myself. Attached is a screen shot of the GVC.DLL dependencies. “crc32\_z” is defined in ZLIB1.DLL, not GVC.DLL. Why is it looking for crc32\_z in the wrong place? ![Graphviz GVC-DLL export functions](https://global.discourse-cdn.com/graphviz/original/2X/8/810e455bb2e65caec921d3906343a0cb5caab9a9.png) Can anyone suggest what’s happening? How do I remedy this? ---
**Author:** ![mark](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/mark/32/84_2.png) [@mark](https://forum.graphviz.org/u/mark)\ **Post date:** [January 30, 2025, 1:10am UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/2 "2025-01-30T01:10:43Z")
crc32\_z sounds like it should be from zlib, not graphviz? [https://github.com/zlib-ng/zlib-ng/blob/a0fa24710c8faa1a746a20cfd5c7c24571e15ca4/crc32.c#L21](https://github.com/zlib-ng/zlib-ng/blob/a0fa24710c8faa1a746a20cfd5c7c24571e15ca4/crc32.c#L21) What’s the stack trace, where did you get precompiled gvc.dll from? Graphviz’s code is open source so you can see it if you want. ---
**Author:** ![smattr](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/smattr/32/85_2.png) [@smattr](https://forum.graphviz.org/u/smattr)\ **Post date:** [January 30, 2025, 8:00am UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/3 "2025-01-30T08:00:57Z")
I don’t know much about Windows linking, but my guess as to what is happening is that your Zlib is \< 1.2.9. The pre-built binaries are probably built against a recent Zlib, taking the first branch of [the following](https://gitlab.com/graphviz/graphviz/-/blob/026cd8d3feda7cbb541c7f13e96c42a905b73e4a/lib/gvc/gvdevice.c#L201-205) during compilation: ```c #if ZLIB_VERNUM >= 0x1290 crc = crc32_z(crc, (const unsigned char*)s, len); #else crc = crc32(crc, (const unsigned char*)s, len); #endif ``` When you try to use this at runtime, it tries to dynamically load `crc32_z` but can’t find this symbol in your Zlib. The dynamic linker that’s responsible for connecting these things has no idea where the `crc32_z` symbol is supposed to come from. It just knows it’s undefined and it needs to find a definition of it _somewhere_. (As I said, this is all just guesswork and may be totally wrong.) ---
**Author:** ![sprezzatura](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/sprezzatura/32/1815_2.png) [@sprezzatura](https://forum.graphviz.org/u/sprezzatura)\ **Post date:** [January 30, 2025, 12:58pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/4 "2025-01-30T12:58:56Z")
I got gvc.dll and zlib1.dll from downloading ver. 12.2.1 from the Graphviz website. The entry point expansion is from a program called Dependency Walker (Microsoft). ---
**Author:** ![sprezzatura](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/sprezzatura/32/1815_2.png) [@sprezzatura](https://forum.graphviz.org/u/sprezzatura)\ **Post date:** [January 30, 2025, 1:09pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/6 "2025-01-30T13:09:33Z")
The zlib1.dll I am using was included from the installation of Graphviz 12.2.1, which was downloaded from the Graphviz website. It is ver. 1.3.1. It appears that “crc32\_z” is not defined in the zlib1.dll. ![Graphviz ZLIB1-DLL export functions](https://global.discourse-cdn.com/graphviz/original/2X/d/d13c6fe0fd1ade3831dd66492cbccbdb9e9dfec5.png) I wish this were simple :o) I would like to avoid having to re-compile the source. Thank you for your reply. ---
**Author:** ![magjac](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/magjac/32/16_2.png) [@magjac](https://forum.graphviz.org/u/magjac)\ **Post date:** [January 30, 2025, 5:46pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/7 "2025-01-30T17:46:09Z")
I just downloaded the zip files for all permutations of Debug/Release and 32/64 bit from [12.2.1 · graphviz / graphviz · GitLab](https://gitlab.com/graphviz/graphviz/-/releases/12.2.1) and analyzed them with dumpbin¹. `crc32_z` seems to be defined in all of them: ```auto magjac@LAPTOP-BT0S5M2L MINGW64 ~/Downloads $ my-dumpbin -exports Debug/Graphviz-12.2.1-win32/bin/zlib1.dll | grep crc 7 6 00001500 crc32 8 7 00001510 crc32_combine 9 8 00001540 crc32_combine_gen 10 9 00001560 crc32_combine_op 11 A 00001580 crc32_z 27 1A 000019A0 get_crc_table magjac@LAPTOP-BT0S5M2L MINGW64 ~/Downloads $ my-dumpbin -exports Debug/Graphviz-12.2.1-win64/bin/zlib1.dll | grep crc 7 6 00001520 crc32 8 7 00001530 crc32_combine 9 8 000015A0 crc32_combine_gen 10 9 000015B0 crc32_combine_op 11 A 000015F0 crc32_z 27 1A 00001AA0 get_crc_table magjac@LAPTOP-BT0S5M2L MINGW64 ~/Downloads $ my-dumpbin -exports Release/Graphviz-12.2.1-win32/bin/zlib1.dll | grep crc 7 6 00001500 crc32 8 7 00001510 crc32_combine 9 8 00001540 crc32_combine_gen 10 9 00001560 crc32_combine_op 11 A 00001580 crc32_z 27 1A 000019A0 get_crc_table magjac@LAPTOP-BT0S5M2L MINGW64 ~/Downloads $ my-dumpbin -exports Release/Graphviz-12.2.1-win64/bin/zlib1.dll | grep crc 7 6 00001520 crc32 8 7 00001530 crc32_combine 9 8 000015A0 crc32_combine_gen 10 9 000015B0 crc32_combine_op 11 A 000015F0 crc32_z 27 1A 00001AA0 get_crc_table ``` ¹ my-dumpbin just points to the installed dumpbin at `C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.42.34433\bin\Hostx64\x64\dumpbin.exe` ---
**Author:** ![magjac](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/magjac/32/16_2.png) [@magjac](https://forum.graphviz.org/u/magjac)\ **Post date:** [January 30, 2025, 6:02pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/8 "2025-01-30T18:02:49Z")
My guess is that you have an older version of zlib1.dll somewhere in your PATH, before your Graphviz install directory. ---
**Author:** ![sprezzatura](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/sprezzatura/32/1815_2.png) [@sprezzatura](https://forum.graphviz.org/u/sprezzatura)\ **Post date:** [January 30, 2025, 8:04pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/9 "2025-01-30T20:04:41Z")
Good news: DUMPBIN does show that the entry point “crc32\_z” is indeed present in zlib1.dll (the version that was included in the Graphviz 12.2.1 installer package): ``` Dump of file F:\Program Files\Graphviz\bin\zlib1.dll File Type: DLL 7 6 00001520 crc32 8 7 00001530 crc32_combine 9 8 000015A0 crc32_combine_gen 10 9 000015B0 crc32_combine_op 11 A 000015F0 **crc32_z** ``` I guess the Dependency Walker program is flawed. So why is gvc.dll not finding it? ---
**Author:** ![sprezzatura](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/sprezzatura/32/1815_2.png) [@sprezzatura](https://forum.graphviz.org/u/sprezzatura)\ **Post date:** [January 30, 2025, 8:13pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/10 "2025-01-30T20:13:41Z")
_\> you have an older version of zlib1.dll somewhere in your PATH_ Excellent suggestion. However, I ran a batch job that looks for “zlib1.dll” in all directories in the PATH. Alas there aren’t any instances of zlib1.dll in any of these directories. As a matter of fact, if I delete or rename the version of zlib1.dll that is in the same directory as my program, then the program complains it can’t find zlib1.dll. So I am indeed calling on the right one. For those who have the source, who is calling the function “crc32\_z”? Is it gvc.dll or someone else? Because the error message implies that whoever is calling it, is looking for it in gvc.dll. ---
**Author:** ![magjac](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/magjac/32/16_2.png) [@magjac](https://forum.graphviz.org/u/magjac)\ **Post date:** [January 30, 2025, 8:51pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/11 "2025-01-30T20:51:29Z")
Then I guess you need to add `F:\Program Files\Graphviz\bin` to your PATH. > For those who have the source, who is calling the function “crc32\_z”? Is it gvc.dll or someone else? As Mark already pointed out, Graphviz is open source. You can find it at [graphviz / graphviz · GitLab](https://gitlab.com/graphviz/graphviz). As Matthew already pointed out, the call to `crc32_z` is in gvc at [lib/gvc/gvdevice.c · 026cd8d3feda7cbb541c7f13e96c42a905b73e4a · graphviz / graphviz · GitLab](https://gitlab.com/graphviz/graphviz/-/blob/026cd8d3feda7cbb541c7f13e96c42a905b73e4a/lib/gvc/gvdevice.c#L201-205). The error message is quite ambiguous, but it most certainly means that the entry point `crc32_z` which is referred to from gvc.dll is not found, i.e., the dynamic linker is resolving symbols “in gvc.dll” when it ascertains “Entry point crc32\_z not found". ---
**Author:** ![sprezzatura](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/sprezzatura/32/1815_2.png) [@sprezzatura](https://forum.graphviz.org/u/sprezzatura)\ **Post date:** [January 30, 2025, 10:48pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/12 "2025-01-30T22:48:11Z")
_\> Then I guess you need to add `F:\Program Files\Graphviz\bin` to your PATH_ Somehow it looks like the version of zlib1.dll that I thought I had copied from Graphviz, was in fact different. The Graphviz one is ver. 1.3.1. The one in my program library was 1.2.8. I don’t know where that one came from. I re-copied the Graphiz one, and now I’m getting a different error that might not be related to Graphviz. Thank you all for your help in walking through this. ---
**Author:** ![sprezzatura](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/sprezzatura/32/1815_2.png) [@sprezzatura](https://forum.graphviz.org/u/sprezzatura)\ **Post date:** [January 31, 2025, 9:42pm UTC](https://forum.graphviz.org/t/entry-point-crc32-z-not-found-in-gvc-dll/2684/13 "2025-01-31T21:42:04Z")
OK, I finally got it going after using the correct zlib1.dll. It;s really neat the way Graphviz can just drop into an existing app and make a whole new presentation. Here’s an ancestor chart that I produce: [http://findyourfamilytree.com/images/test4.pdf](http://findyourfamilytree.com/images/test4.pdf) Download the PDF and view it with Adobe Reader, the browser PDF viewer doesn’t do it justice. [http://findyourfamilytree.com/images/test.svg](http://findyourfamilytree.com/images/test.svg) The source can be seen here: [http://findyourfamilytree.com/images/test.gv](http://findyourfamilytree.com/images/test.gv). At 197KB, I suspect it’s too big to be posted inline. The crossed lines are due to pedigree collapse (implexus): when distant cousins inter-marry. I can’t display it inline because the rendering engine can’t handle escaped quotes in labels.