From 7bbeb8bd694a1bc3f71484880f664325488816ae Mon Sep 17 00:00:00 2001
From: jolavillette <jolavillette@gmail.com>
Date: Mon, 17 Aug 2026 09:39:38 +0200
Subject: [PATCH] Android: tell libtiff where libm is

tiff cmake/FindCMath.cmake probes pow(3) twice, first with no extra
library then with the result of find_library(NAMES m). On Android pow is
in libm, and the NDK keeps libm.so under the API level directory of the
sysroot, sysroot/usr/lib/<triple>/<api>/, which andro_cmake does not add
to CMAKE_LIBRARY_PATH. find_library returns NOTFOUND, the second probe
links exactly like the first one and both fail with

  ld.lld: error: undefined symbol: pow

so configure aborts on

  Could NOT find CMath (missing: CMath_pow)

taking build_cimg and build_phash down with it.

Pass CMath_LIBRARY explicitly rather than adding the API level directory
to the search path of every dependency, which would change how the other
ten already working ones resolve their libraries.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 misc/Android/prepare-toolchain-clang.sh | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/misc/Android/prepare-toolchain-clang.sh b/misc/Android/prepare-toolchain-clang.sh
index 43f2103de..9e3d0f559 100755
--- a/misc/Android/prepare-toolchain-clang.sh
+++ b/misc/Android/prepare-toolchain-clang.sh
@@ -749,11 +749,21 @@ build_tiff()
 
 	pushd $B_dir
 	#TODO: build dependecies to support more formats
+	# tiff cmake/FindCMath.cmake looks for pow(3) first without any library
+	# then with whatever find_library(NAMES m) returned. On Android pow lives
+	# in libm, and libm is under the API level directory of the NDK sysroot,
+	# which andro_cmake does not put in CMAKE_LIBRARY_PATH, so find_library
+	# comes back empty, the second check links without -lm just like the first
+	# one and configure aborts with
+	#   Could NOT find CMath (missing: CMath_pow)
+	# Give it the library explicitly instead of widening the search path for
+	# every dependency.
 	andro_cmake \
 		-DBUILD_SHARED_LIBS=OFF \
 		-Dlibdeflate=OFF -Djbig=OFF -Dlzma=OFF -Dzstd=OFF -Dwebp=OFF \
 		-Djpeg12=OFF \
 		-Dcxx=OFF \
+		-DCMath_LIBRARY="${SYSROOT}/usr/lib/${compilerTriple}/${ANDROID_PLATFORM_VER}/libm.so" \
 		-B. -S../$S_dir    || return $?
 	make -j${HOST_NUM_CPU} || return $?
 	make install           || return $?