### Project Definition and Library Setup

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Configures the project name and library name. It handles both included and stand-alone usage scenarios, finding the library and setting the build type.

```cmake
if(PROJECT_NAME)
    set(LIBRARY_NAME ${PROJECT_NAME})
else()
    # Define an independent project and all the necessary stuff around
    project(${LTM_TEST}
        LANGUAGES C)
    set(LIBRARY_NAME libtommath)
    find_package(${LIBRARY_NAME})
    include(CTest)
    if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
        set(CMAKE_BUILD_TYPE "Release")
    endif()
endif()
```

--------------------------------

### Verify GNU Libtool Version

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Command to check the version of the GNU libtool installed, differentiating it from the native libtool.

```shell
$ /usr/local/bin/libtool --version                              
libtool (GNU libtool) 2.4.2
Written by Gordon Matzigkeit <gord@gnu.ai.mit.edu>, 1996

Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

```

--------------------------------

### Build LibTomMath with CMake

Source: https://github.com/libtom/libtommath/blob/develop/README.md

Clone the repository, create a build directory, and use CMake to configure the build. Use 'make -j$(nproc)' to compile. A shared library can be built by setting -DBUILD_SHARED_LIBS=On.

```bash
git clone https://github.com/libtom/libtommath.git
mkdir -p libtommath/build
cd libtommath/build
cmake ..
make -j$(nproc)
```

--------------------------------

### Build Shared Library with Libtool

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Use this command to build the shared library of LibTomMath when libtool is available.

```bash
LIBTOOL="/usr/local/bin/libtool" gmake -f makefile.shared
```

--------------------------------

### S390x CPU Information

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Displays vendor information for an S390x system running Debian.

```bash
user@debians390x:~/GITHUB/libtommath$ cat /proc/cpuinfo 
vendor_id       : IBM/S390

```

--------------------------------

### OpenBSD Make Parse Errors

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Illustrates common parse errors encountered when using the wrong 'make' utility on OpenBSD, preventing shared library builds.

```makefile
*** Parse error in /home/user/GITHUB/libtommath: Need an operator in 'LIBNAME' )
*** Parse error: Need an operator in 'endif' (makefile.shared:8)
*** Parse error: Need an operator in 'CROSS_COMPILE' (makefile_include.mk:16)
*** Parse error: Need an operator in 'endif' (makefile_include.mk:18)
*** Parse error: Missing dependency operator (makefile_include.mk:22)
*** Parse error: Missing dependency operator (makefile_include.mk:23)

```

--------------------------------

### MIPS CPU and System Information

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Displays CPU information, kernel version, and byte order for a MIPS Malta system running Debian.

```bash
$ cat /proc/cpuinfo 
system type		: MIPS Malta
machine			: mti,malta
processor		: 0
cpu model		: MIPS 24Kc V0.0  FPU V0.0
BogoMIPS		: 688.12
wait instruction	: yes
microsecond timers	: yes
tlb_entries		: 16
extra interrupt vector	: yes
hardware watchpoint	: yes, count: 1, address/irw mask: [0x0ff8]
isa			: mips1 mips2 mips32r1 mips32r2
ASEs implemented	: mips16
shadow register sets	: 1
kscratch registers	: 0
package			: 0
core			: 0
VCED exceptions		: not available
VCEI exceptions		: not available
$  uname -a
Linux debianmips32 4.9.0-8-4kc-malta #1 Debian 4.9.144-3.1 (2019-02-19) mips GNU/Linux
$ gcc -dM -E -x c /dev/null | grep BYTE_ORDER
#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
$ gcc -dM -E -x c /dev/null | grep LDBL
#define __LDBL_MAX__ 1.7976931348623157e+308L
#define __LDBL_MAX_EXP__ 1024
#define __LDBL_HAS_INFINITY__ 1
#define __LDBL_MIN__ 2.2250738585072014e-308L
#define __LDBL_HAS_QUIET_NAN__ 1
#define __LDBL_HAS_DENORM__ 1
#define __LDBL_EPSILON__ 2.2204460492503131e-16L
#define __LDBL_MANT_DIG__ 53
#define __LDBL_MIN_EXP__ (-1021)
#define __LDBL_MAX_10_EXP__ 308
#define __LDBL_DENORM_MIN__ 4.9406564584124654e-324L
#define __LDBL_MIN_10_EXP__ (-307)
#define __LDBL_DIG__ 15

```

--------------------------------

### Find and Configure Valgrind for Memory Checking

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Locates the 'valgrind' executable and sets options for memory checking, including tracing child processes and performing a full leak check.

```cmake
find_program(MEMORYCHECK_COMMAND valgrind)
set(MEMORYCHECK_COMMAND_OPTIONS "--trace-children=yes --leak-check=full")
```

--------------------------------

### Sparc64 Debian Build Information

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Shows system information and GCC preprocessor definitions for long double on a Sparc64 Debian system. Useful for understanding floating-point representation.

```shell
cpu		: TI UltraSparc IIi (Sabre)
fpu		: UltraSparc IIi integrated FPU
pmu		: ultra12
prom		: OBP 3.10.24 1999/01/01 01:01
type		: sun4u
ncpus probed	: 1
ncpus active	: 1
D$ parity tl1	: 0
I$ parity tl1	: 0
Cpu0ClkTck	: 0000000005f5e100
cpucaps		: flush,stbar,swap,muldiv,v9,mul32,div32,v8plus,vis
MMU Type	: Spitfire
MMU PGSZs	: 8K,64K,512K,4MB

```

```shell
$ uname -a
Linux debiansparc64 4.15.0-2-sparc64 #1 Debian 4.15.11-1 (2018-03-20) sparc64 GNU/Linux

```

```shell
$ gcc -dM -E -x c /dev/null | grep BYTE_ORDER
#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__

```

```shell
$ gcc -dM -E -x c /dev/null | grep LDBL
#define __LDBL_MAX__ 1.18973149535723176508575932662800702e+4932L
#define __LDBL_MAX_EXP__ 16384
#define __LDBL_HAS_INFINITY__ 1
#define __LDBL_MIN__ 3.36210314311209350626267781732175260e-4932L
#define __LDBL_HAS_QUIET_NAN__ 1
#define __LDBL_HAS_DENORM__ 1
#define __LDBL_DECIMAL_DIG__ 36
#define __LDBL_EPSILON__ 1.92592994438723585305597794258492732e-34L
#define __LDBL_MANT_DIG__ 113
#define __LDBL_MIN_EXP__ (-16381)
#define __LDBL_MAX_10_EXP__ 4932
#define __LDBL_DENORM_MIN__ 6.47517511943802511092443895822764655e-4966L
#define __LDBL_MIN_10_EXP__ (-4931)
#define __LDBL_DIG__ 

```

--------------------------------

### Verify Native Libtool Version

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Command to check the version of the native libtool, distinguishing it from the GNU version.

```shell
$ libtool --version
libtool (not (GNU libtool)) 1.5.26

```

--------------------------------

### Set Include Directories for Test Executable

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Configures include directories for the test executable. It includes the current source directory and a conditional include for the parent directory when the project name matches the test name.

```cmake
target_include_directories(${LTM_TEST} PRIVATE
    ${CMAKE_CURRENT_SOURCE_DIR}
    $<$<STREQUAL:${PROJECT_NAME},${LTM_TEST}>:${CMAKE_CURRENT_SOURCE_DIR}/..>
)
```

--------------------------------

### Link Test Executable to Library

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Links the test executable against the main library, specified by LIBRARY_NAME. This makes the library's functionality available to the test program.

```cmake
target_link_libraries(${LTM_TEST} PRIVATE
    ${LIBRARY_NAME}
)
```

--------------------------------

### Create Test Executable Target

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Defines an executable target named by LTM_TEST, linking the shared.c and test.c source files.

```cmake
add_executable(${LTM_TEST}
    ${CMAKE_CURRENT_SOURCE_DIR}/shared.c
    ${CMAKE_CURRENT_SOURCE_DIR}/test.c
)
```

--------------------------------

### OpenBSD Libtool Linking Errors

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Shows typical linking errors that occur when the incorrect 'libtool' is used on OpenBSD, leading to build failures for shared libraries.

```shell
cc -I./ -Wall -Wsign-compare -Wextra -Wshadow -Wsystem-headers -Wdeclaration-afo...
cc -I./ -Wall -Wsign-compare -Wextra -Wshadow -Wsystem-headers -Wdeclaration-afo...
cc -I./ -Wall -Wsign-compare -Wextra -Wshadow -Wsystem-headers -Wdeclaration-afo...
libtool --mode=link --tag=CC cc  bn_error.lo bn_fast_mp_invmod.lo bn_fast_mp_mo
libtool: link: cc bn_error.lo bn_fast_mp_invmod.lo bn_fast_mp_montgomery_reduce0
bn_error.lo: file not recognized: File format not recognized
cc: error: linker command failed with exit code 1 (use -v to see invocation)
Error while executing cc bn_error.lo bn_fast_mp_invmod.lo bn_fast_mp_montgomery0
gmake: *** [makefile.shared:64: libtommath.la] Error 1

```

--------------------------------

### Set Linker Options for Test Executable

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Adds linker flags to the test executable. These flags are applied before other public link options.

```cmake
target_link_options(${LTM_TEST} BEFORE PUBLIC
    ${LTM_LD_FLAGS}
)
```

--------------------------------

### Check Byte Order

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

This command checks the byte order of the system using GCC preprocessor directives. It is useful for understanding endianness which can affect binary data handling.

```bash
user@debians390x:~/GITHUB/libtommath$ gcc -dM -E -x c /dev/null | grep BYTE_ORDER
#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
```

--------------------------------

### Set Compile Options for Test Executable

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Applies compile-time options to the test executable. It conditionally defines LTM_TEST_DYNAMIC if the library is a shared library.

```cmake
target_compile_options(${LTM_TEST} PRIVATE
    $<$<STREQUAL:$<TARGET_PROPERTY:${LIBRARY_NAME},TYPE>,SHARED_LIBRARY>:-DLTM_TEST_DYNAMIC>
    ${LTM_C_FLAGS}
)
```

--------------------------------

### Error Handling with Goto

Source: https://github.com/libtom/libtommath/wiki/The-Sourcecode:-Formatting-and-Style

Error handling is typically done using a goto statement to a common error-handling section at the end of the function. The goto statement should be on the same line as the error check and aligned.

```c
if ((err = mp_add(&a, &b, &c) != MP_OKAY)        goto LTM_ERR;
if ((err = mp_incr(&c) != MP_OKAY)               goto LTM_ERR;
```

--------------------------------

### Set Minimum CMake Version

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Specifies the minimum version of CMake required for this project. Ensures compatibility with required features.

```cmake
cmake_minimum_required(VERSION 3.10)
```

--------------------------------

### Intel Compiler Warnings

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

This output shows diagnostic warnings from the Intel compiler (ICC) regarding unsupported GCC diagnostic options. It suggests a workaround to suppress these warnings.

```text
icc: command line warning #10148: option '-Wbad-function-cast' not supported
icc: command line warning #10148: option '-Wcast-align' not supported
```

--------------------------------

### Define Test Executable Name

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Sets a variable for the name of the test executable. This is used later when creating the executable target.

```cmake
set(LTM_TEST test-ltm)
```

--------------------------------

### Add CTest Test

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Defines a CTest test case that runs the compiled test executable. This integrates the test into the CMake testing framework.

```cmake
add_test(NAME ${LTM_TEST} COMMAND ${LTM_TEST})
```

--------------------------------

### Check Double/Long Double Precision on Debian ARM

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

Verifies if double and long double have the same precision on a Debian ARM system. This is relevant for platforms where `double == long double`.

```c
#include <stdio.h>
#include <stdlib.h>
#include <float.h>

int main (void) {
   printf("%d == %d  %d == %d\n",
           LDBL_MANT_DIG, DBL_MANT_DIG,
           LDBL_MAX_EXP,  DBL_MAX_EXP);
   exit(EXIT_SUCCESS);
}

```

```shell
$ ./dbl_print 
53 == 53  1024 == 1024

```

```shell
$ uname -a
Linux debian 3.16.0-6-versatile #1 Debian 3.16.57-2 (2018-07-14) armv5tejl GNU/Linux

```

```shell
$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 8.11 (jessie)
Release:        8.11
Codename:       jessie

```

```shell
$ cat /proc/cpuinfo
processor       : 0
model name      : ARM926EJ-S rev 5 (v5l)
BogoMIPS        : 500.22
Features        : swp half thumb fastmult vfp edsp java 
CPU implementer : 0x41
CPU architecture: 5TEJ
CPU variant     : 0x0
CPU part        : 0x926
CPU revision    : 5

Hardware        : ARM-Versatile PB
Revision        : 0000
Serial          : 0000000000000000

```

--------------------------------

### Configure Debug CFLAGS

Source: https://github.com/libtom/libtommath/blob/develop/demo/CMakeLists.txt

Sets compiler flags for debug builds, specifically for non-MSVC compilers. Includes debug symbols and optimization level 1.

```cmake
if(NOT MSVC)
    set(CMAKE_C_FLAGS_DEBUG "-g3 -O1")
endif()
```

--------------------------------

### Conditional Statement Parentheses

Source: https://github.com/libtom/libtommath/wiki/The-Sourcecode:-Formatting-and-Style

Use parentheses for individual statements within an if expression for clarity. This applies to complex boolean conditions.

```c
if ((a > 0) && (a < 42) && ((a & 0x1) == 0)) ...
```

--------------------------------

### Check Long Double Max Value

Source: https://github.com/libtom/libtommath/wiki/Successes-and-Failures-of-Building-LibTomMath

This command uses GCC to display the maximum value and related properties of the long double type. This information is relevant for understanding the precision and range of floating-point calculations.

```bash
user@debians390x:~/GITHUB/libtommath$ gcc -dM -E -x c /dev/null | grep LDBL
#define __LDBL_MAX__ 1.18973149535723176508575932662800702e+4932L
#define __LDBL_MAX_EXP__ 16384
#define __LDBL_HAS_INFINITY__ 1
#define __LDBL_MIN__ 3.36210314311209350626267781732175260e-4932L
#define __LDBL_HAS_QUIET_NAN__ 1
#define __LDBL_HAS_DENORM__ 1
#define __LDBL_EPSILON__ 1.92592994438723585305597794258492732e-34L
#define __LDBL_MANT_DIG__ 113
#define __LDBL_MIN_EXP__ (-16381)
#define __LDBL_MAX_10_EXP__ 4932
#define __LDBL_DENORM_MIN__ 6.47517511943802511092443895822764655e-4966L
#define __LDBL_MIN_10_EXP__ (-4931)
#define __LDBL_DIG__ 33
```

--------------------------------

### Excessive Parentheses Avoidance

Source: https://github.com/libtom/libtommath/wiki/The-Sourcecode:-Formatting-and-Style

Avoid overly nested or redundant parentheses in arithmetic expressions. Keep expressions clear and concise.

```c
a = x + (y * z);
b = (((a + (b / c)) - (d * e)) + (3 / 2));
c = (x - y) - z;
```

--------------------------------

### Assignment in If Clause for Error Handling

Source: https://github.com/libtom/libtommath/wiki/The-Sourcecode:-Formatting-and-Style

Assignments within an if() clause are permitted only for error checking during error handling. This is an exception to the general rule against assignments in if conditions.

```c
if ((err = mp_add(&a, &b, &c) != MP_OKAY)        goto LTM_ERR;
```

--------------------------------

### Ternary Operator Parentheses

Source: https://github.com/libtom/libtommath/wiki/The-Sourcecode:-Formatting-and-Style

Enclose the conditional statement in a ternary operator within parentheses. This ensures correct evaluation order.

```c
a = (b < 0) ? -1 : 1;
```

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