RE: Strange problem when compiling sscanRecord.c on Windows

[Freddie Akeroyd - STFC UKRI via Tech-talk <tech-talk at aps.anl.gov>]

Hi Mark,

 

If you set whole program optimisation to NO (   https://github.com/epics-base/epics-base/blob/ac0fc2effff43c9db116ae68c91f3a9767c991ec/configure/os/CONFIG.win32-x86.win32-x86#L13 )

 

   does it speed things up for windows-x64? For windows-x64-static this should already be disabled via  https://github.com/epics-base/epics-base/blob/ac0fc2effff43c9db116ae68c91f3a9767c991ec/configure/os/CONFIG_SITE.Common.windows-x64-static#L8

 

Regards,

 

Freddie

 

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Mark Rivers via Tech-talk
Sent: 01 May 2026 19:16
To: EPICS Tech Talk <tech-talk at aps.anl.gov>
Subject: Strange problem when compiling sscanRecord.c on Windows

 

Folks,

 

I have noticed that compiling the EPICS scan record (https://github.com/epics-modules/sscan/blob/master/sscanApp/src/sscanRecord.c) is extraordinarily slow on Windows with Visual Studio.

 

This is my environment:

Base 7.0.10

Visual Studio compiler version: Microsoft (R) C/C++ Optimizing Compiler Version 19.44.35215 for x64

sscanRecord version: master branch in the link above.

 

I tested by deleting all of the xxxRecord.obj files in the O.windows-64 or O.windows-x64-static directories and then timing how long it took "make" to complete.  This is the time to both compile the xxxRecord.c files and the time to link the relevant library.  "make" was run without the -j option, so the build was sequential, not parallel.

 

The following table compares the time to compile and link the relevant library for a number of EPICS records on both static builds (windows-x64-static) and dynamic builds (windows-x64).

 

Files	Total lines of C code	Time (s) for windows-x64	Time (s) for windows-x64-static
All 34 record files in base/modules/database/src/std/rec	13,369	54	59
All 5 record files in calc/calcApp/src	5,460	30	23
sscanRecord.c	5,596	242	251

 

This is what I see with Windows TaskManager when compiling sscanRecord.c and linking the library:

• On  windows-x64-static the compiler (cl.exe) is using 100% of a core for most of the 251 seconds.

• On windows-x64 the linker (link.exe) is using 100% of a core for most of the 242 seconds.

 

This seems very strange to me.  It is taking 8-10 times longer to compile and link sscanRecord.c than it does to compile and link essentially the same number of lines of record code for the 5 records in calcApp.

 

Any ideas?

 

Thanks,

Mark